So... I decided to do a LoL-to-Dota2 writeup, based on my own experiences. Hopefully, it can help some LoL players struggling with Dota mechanics/gameplay. I'm by no means an expert, mind you... Please correct me where I'm wrong. I played Dota a long time ago, then quit, then played intensive LoL for the last couple of years, and now I permanently moved to Dota2. This post is not about which games is better, more fun, or whatever. I'm only trying to help people making the switch.

Now, everyone knows the mechanical differences, but how these differences really affect the gameplay is what it's important

Things Dota2 has:
+ Gold loss on death
+ Denying
+ Courier
+ Teleport scrolls
+ Many more items with active abilities
+ Bigger map
+ LoS juking
+ Larger range of abilities, in general.
+ Runes

Things Dota2 doesn't have:
- Free teleport to base
- Summoner metagame (runes, masteries, spells)
- Brush
- Jungle buffs
- Ability Power / Ability scaling with items (ability damage is fixed)
- Very powerful Towers

Now, these seemingly short list of differences imply a lot of changes in mechanics, the metagame, and the way the game is played.

So, I'll try to explain how things change from both a mechanical and subjective point of view, and the mindset change required to play effectively.

- Gold Management and Lane Control
Let's start with gold management. In LoL it's very very easy. You last hit creeps or kill enemy champions, you get gold. You save towards an item, you teleport back to base and you get it, ready to rejoin the fray.

In Dota things get a bit more complicated...
* First of all, you lose gold on death. This means that dying repeatedly is way more punishing. You not only feed your enemy, you gimp yourself further and further, becoming more likely to keep dying, as you can never get enough items to put up a good fight.

* You can't just hoard money for your Big Item. You have to plan carefully, and buy the most useful smaller components as you go. This seemingly obvious thing is ignored a lot more than people like to admit (by LoL players, at least)... I can clearly remember League matches with people claiming "lol I have 3k, forgot to buy...". Unless the enemy are idiots that can't kill you even when you don't have items, this is highly unlikely in Dota2. This example is exaggerated, but really... Spend your money. (Even if you're not going immediately to base... See "Stash" below). Now, there are some items that need saving and are core to a hero/build (Blink Dagger for Earthshaker, for example). If you need to save this much money it's imperative you don't die, of course, or the setback will keep you from doing what your team expects from you for another couple of teamfights, and you need to go farm instead of being where your team needs you. Dying while saving big money can be game changing. Be extra careful.

* Side Lane Shop: This is related both to gold management and no free teleport (and also lane control)... In regards to gold management, it's related to not hoarding. If you're going for an item the side shop has (boots or some small components for eary/mid game items), buy it as soon as you have the money (and you have good lane control to actually reach the shop safely and without the enemy knowing). Plan your item strategy considering what you can get from the side shop, and what you'll have to get from the base shop. Try and stay in lane so everything go as planned and you only go back when you decide to, and not because you're forced to.

* Stash: Also related to not hoarding and the lack of free teleport... Good use of the stash is vital in gold/item management. At first you'll probably won't use it for late game item switching, but you should be using it right now to get base shop items as soon as you have the money, even if you don't plan on going back to base soon. If you die, your item will be safe in the stash, and you won't have lost the money you spent to get it. Of course, you can also use the courier (See Courier below)

* Also related to the lack of free teleport... Teleport scrolls: These cost 135g, and you should always keep at least one with you, but, particularly in early game, you shouldn't use them just because they're convenient... They're too expensive early game, and you will gimp yourself if you spend all your money jumping around the map. Use them when it truly matters (setting up a quick gank on a lane, or helping to avoid one, or to stop a push, etc)

* The courier also plays an important role in gold management/lane control. First of all, the designated support hero should spend the money to get it (170g). This will most likely be the hero warding the map also. If you only have 1 courier, then the mid hero probably should have priority (I say probably, because there are many valid lane setups in Dota in which this may not be the best choice). But with smart timing, you can get use of the courier as well, if you're side laning. The courier is vital in avoiding long trips to the base, or having to spend money on extra teleport scrolls. The courier can be used as any other unit (default key to select it: F2), and you should be careful what you do with it. Don't get it killed. The items will drop and the enemy will be able to pick them up. One thing you should learn is the F2-E-D(-F) shortcut combo.
F2: Selects the courier (without focusing it, so you keep the camera where your hero is at)
E: Picks up all the stuff you have in the stash
D: Orders the courier to bring those items to you.
F: Only when upgraded to flying courier, this will boost its speed for a short time (it has a cooldown)

This very fast sequence of keys (F2,E,D) will tell the courier to bring your stuff, while you don't lose vision and focus on your hero. BE CAREFUL THO. Don't just forget about the courier while he's coming to you. It might get killed in the way... Be mindful of your movements, because the courier will change its pathing (which can be very dangerous for non-flying ones) to adjust to your new position. Also: Respect other people use of the courier... Don't just mindlessly send these orders to the courier. Check first what's going on, and if someone with top priority is getting something delivered... If you feel you should have the priority for a certain delivery, warn your teammates you're overriding their orders, and why... Don't be a jerk fighting over a courier.

* Farming and Denying: In LoL, good players strive to deny experience and farm with positioning and harassing. On side lanes, gaining an advantage in the brush is vital. In Dota2 there's no brush, and positioning is everything. Hiding from view is accomplished by using LoS blocking with trees (LoS: Line of Sight). Apart from harassing and threatening the enemy with good positioning and smart spell use, you can and should deny minions. The skill required to do this is the same as last hitting. If you can last hit properly, you will be able to deny properly. Don't just ignore your almost dead creeps to get a last hit... 2 denies are probably better than 1 last hit. It all depends on your hero of course... A carry should last hit as much as possible, whereas a support can concentrate on denying and harassing and creating breathing room for his carry.

* Couriers and teleport scrolls management are essential to lane control as well. Keep an eye on the river and the side shop. This is doubly important if you're Radiant top tower, or Dire bot (As you've seen, Dota2 map is symmetrical(ish) globally, but not samelane-wise).

* Regen: I'm not going to delve into item builds here, as this is only a LoL-to-Dota post, but let me tell you just this: Regen is much more important in Dota2 than LoL. Health or mana potions are mostly ignored in LoL unless you're jungling, and people always forget to use them. In Dota2 your lane control will suck if you don't have good regen. Clarity potions are essential for mana intensive heroes early on if you want to actually get some use of your abilities. Carries need tangos/salves to be able to withstand some harassing when going for last hits, and so on with every single role. Dota's default regen rate is very low compared to LoL, where you can stand in the brush for a while and heal up

* Runes: Starting with the first creep wave spawn, a rune will spawn every 2 minutes in either the top or bottom side of the river. Getting control of these runes gives your team an important advantage, no matter what stage of the game you're at. Early game they're commonly used for ganking. As a side laner you must try & check for runes, keeping in mind who can get the best use of it (Check for runes, but don't always get them. Your mid will probably get more use of it ganking). 0 minute rune checking can produce early fights, so be careful when going for them (Consider this like starting with a blue jungler in LoL, where the rest of your team guards you). Check the rune types in playdota.com to see their effects. Know em and understand them. They're more diverse than LoL's monster buffs.

- Items

* You'll have to learn to understand and use items. Lots of them, with many different abilities. This is something many LoL-comers struggle with at first. Consider them as part of your arsenal of abilities. In fact, some heroes rely on some items so much that they're normally thought of as always having them, and if you don't, you'll be called a noob. You're warned. Blink Dagger for Earthshaker or Sand King is an obvious example of this.

* Mana management: Abilities in Dota2 are much more powerful than in LoL, but normally cost a lot more mana. Powerful abilities by casters can be used maybe twice at level 1. Melee/non caster oriented heroes might only have one use worth of mana. Not using an ability to its full potential can be a very bad thing. LoL is designed to let you spam abilities "because it's fun", so you can use them like crap and don't care. In Dota2 you can't freely harass with spells. Only do it when it counts. Eventually the issue switches to cooldowns, but early game, learn to manage your mana properly. (This is one of the reasons Lich is normally recommended as a good starting hero... He doesn't have as many mana problems thanks to sacrifice)

- The not so obvious stuff.
So, that was all pretty much about mechanics, with some abstract concepts thrown in. Now let's go completely abstract, into the mindset / decision making process differences of LoL and Dota2. This is the kind of thing LoL players have the most trouble with, and it's understandable why...

1st rule: The "minimum safety distance" is much much larger in Dota2 (Meaning, in LoL you could be less than half a screen apart from 2 champions and be safe, in Dota2 you're asking for trouble). Of course, it all depends on the hero and whether he has an escape mechanism and how good the player is, but in general, keep your distance (when not having the advantage, i mean). Move a lot. Use the trees for LoS hiding. Abilities have a very large range. You can get easily stunned from afar. There are a gazillion long range disables in Dota2. If you are disabled for say, 2 seconds, with 2 heroes "nearby", you'll die (unless your hero has a good escape ability and/or you're a skilled player, but if you're a struggling LoL-comer then you'll die). This also relates to not having Flash/Ghost... Don't just frantically look for that magical spell that will save your ass if you're in trouble. Keep your focus and use your abilities/items. Fight. Learn to survive. And if you die, learn the lesson. Keep your distance and know the enemy abilities.

2nd rule: The towers won't save your ass. LoL towers are so much more powerful than Dota2, and they'll switch targets very quickly to help you. Tower diving is deadly for the diver in LoL for the first few levels (and can result in a death even past level 6). In Dota2 diving is very viable, and getting a couple of hits from towers is not a (very) big deal. That means that you can't just stand in front of your tower and laugh at those 2 hereos apparently keeping their distance. In fact, defend towers, but don't even consider them a "stronghold". Keep your distance behind them as if they weren't there. They'll dive and kill you, and if you say "WTF Tower?" people will laugh at you.

3rd rule: Don't wander the jungle alone and in risky areas unless you can see all 5 enemies on the minimap, and even so, mind where you go. Jungle paths are not as clearly defined as in LoL, and there a lot of hiding/juking spots. Study the map. Create a practice game and walk it up and down the whole way, several times. Know the "hidden" paths. See how your LoS changes. Pull neutral camps and juke them. Buy a hatchet and look for spots where destroying a single tree can open up a new path or a hiding area. Know and understand the map. This will make you so much better at Dota2, not only because you'll be able to juke and fight more effectively in the jungle, but also because you'll be able to predict enemy movement.

4th rule: Don't overextend. This also applies to LoL, of course, but since you don't have free escape mechanisms, overextending will get you killed a lot more in Dota. If you're all alone past the river, and you can't see all 5 enemies in the minimap (at a safe distance), then you're most likely overextending. Of course, depending on map control, you can overextend even on your side of the river. Try and draw an imaginary "safe" line you shouldn't cross alone without full enemy visibility in the minimap, and stick to the rule (all of this of course, while you're still learning the game... ). The line can be the river at the beginning, but will move when the game progresses, and it won't be straigth. Overextending also applies to chasing... First of all, you should never chase alone unless you know you can get a kill very fast, and have a quick escape mechanism to avoid the incoming enemy help. Don't chase blindly and for a long time. If the fleeing enemy enters the jungle, stop chasing unless you know exactly what you're doing. Jungle chasing alone will get you killed if you go at it the LoL-way.

Oh, and one more thing... Fed carries can be even more devastating in Dota2 than LoL, but they can also be more easily shut down thanks to the sheer amount of disables. It takes coordination and good teamwork to chain-disable a fed anti-mage long enough to kill him, but it's doable. So, if you somehow get fed, don't think you're some kind of Tryndamere that can right click his way to rampage while drinking a glass of wine. Even an anti-mage killing everyone here and there is using his abilities all the time, to blink in and out, etc. Right clicking heroes just doesn't work very well in Dota2.