TIPS:

Aim for the head. You'll do usually around twice the damage.

Difficulties are Normal, Hard, Very Hard, Overkill and Death Wish. Death Wish missions are unlocked after you hit level 80 and require considerably more skill and effort than the rest.

There are several types of cops in the game. The most often used terms are swats, greens, tans and elites. Swats are the ones in blue armor, greens are the ones in -unsurprisingly- green armor, tans are the ones with tan ceramic armor plates and elites are ones with gray digital camo. Elites only spawn on the Death Wish difficulty.

Your armor recharges, your health does not. Use the downtime while taking cover to reload your weapons.

CAR-4 is a direct upgrade to AMCAR and is an extremely versatile weapon applicable to all situations. A good starter weapon for new players.

Grenades from asset case or Weapon Pack #1 are most useful for stunning specials or clutch area-of-denial. The damage they deal isn't as impressive.

Tan cops take no damage if you hit the tan ceramic armor plates. Headshots are most effective, flanking works too.

Bulldozers do take damage to the body, but with the massive 5500 health pool it's nigh-impossible to kill them without shooting at the exposed face and taking advantage of their 22x headshot multiplier.

You defeat tasers by either killing them from far away or very close-up. Being tased mid-range makes hitting them hard. Note that you can still voluntarily shoot your weapon while being tased.

Shields are countered with flanking. Shield-piercing sniper riflers are preferable (or shotgun slugs, but that is not as effective). If you lack both, grenades and Iron Man ace from enforcer tree stagger them.

Cloakers... You just have to spot them before they spot you. Booby-trapping air vents with trip mines works wonders.

Shooting a camera causes a guard to path to it. If he sees a broken camera, (most of the time) he will become alerted. This works even if the camera operator is down.

Most maps with cameras also have a camera room behind a security door. Killing the guard inside will deactivate cameras.

Shotguns with silencers launch bodies. Sometimes during stealth you can shoot the body into a corner to minimize the risk of being seen or altogether eliminate it.

All silencers are equal. The mechanic for "loudness" was too hard to gauge so Overkill scrapped it.

Tier bonuses just require you to unlock that tier. No need to spend points in that specific tier.

When making a stealth-goes-bad loadout, if you can choose between high-concealment weapons and heavy armor or lower concealment weapons but less armor, always take the latter. It doesn't matter if you can soak damage, you're not killing anyone with the two high-concealment peashooters.

Base+mod accuracy caps at 18 and base+mod stability caps at 25. Skill bonuses can raise the stats above these caps. For snipers both are practically useless, aiming down sights reduces the spread to zero and the rate of fire is so slow that the recoil will always be negated before you can take another shot.

Accuracy (especially excessive accuracy) is bad for shotguns, as it reduces the pellet spread. (Despite what some say, shotguns shoot pellets, not a "cone of damage".) Only the most damaging pellet actually damages the enemy, so a wider spread increases your chances of hitting the head and/or other enemies. Mosconi with 0 accuracy is a bit overkill, and can sometimes miss its targets even if they're close.

Killing enemies hastens the end of the assault wave. More specifically, killing ENOUGH cops ends the assault wave. There's a separate timer which will end the assault wave even if you haven't killed enough. Special kills count as multiple normal kills.

Hostages extend the breaks between waves. A single hostage delays the assault by 30 seconds (10 seconds on Death Wish), and any further hostages have no effect.

Damage breakpoints are more important than any other stat on a gun. Extra damage by itself is only marginally useful if it doesn't count towards reaching the next breakpoint.

That has to do with shots-to-kill. A weapon which does 99 damage and a weapon which does 50 damage are equally effective if the enemy has 100 health. You have to shoot twice with both weapons, the 99-dmage one just wastes 98 points of the damage of the second shot.

40, 50 and 100 damage are the most important ones. 40 one-shots green cops in the head, and 50/100 two/one-shots tan cops in the head. Technician Tier 4 has 25% headshot damage bonus, which makes headshots with 40/80-damage weapons equal to 50/100-damage ones.

On Overkill and below the breakpoints are 20, 25, 34, 40, 50, and 100 damage. Aim for these, then accuracy/stability, whichever you think is in worse shape, then extra damage and then threat.

Threat increases the chance of enemies diving to cover or ducking. Nothing else.

Concealment and detection risk are inversely proportional. Concealment has no cap, but the minimum detection risk is three. Higher concealment makes the detection meter start lower, climb slower and after losing line of sight it also disappears faster. It also vastly reduces the distance at which you are detected.

You can join DLC heists without owning the DLC first. DLC-only Grenade Case asset can be used by everyone.

Ammo bags cannot be wasted by just using them. If you're missing 10% of your total ammo you'll use up half as much of the ammo bag than someone who is missing 20% of his total ammo.

Medkits don't work like that. One use equals one charge removed from the medkit. You can see the charges remaining in a medkit by looking at the amount of blood bags inside one.

Medkits also reset the custody counter. If you go down four times in a row, you'll be instantly brought into custody. If medkits are scarce don't use them just to refill your health, save them for when your vision is black-and-white. That's a sign of you being downed thrice in a row.