BACK UP YOUR SAVES: PC save data's in My Documents/My Games/EDF4.1, hackers in online multiplayer have been known to instantly unlock everybody's weapons and give them shittons of health so keep a few backups on hand, easily done with 7zip in a few keystrokes or with third-party programs for automatic backup.

Manual: http://cdn.akamai.steamstatic.com/steam/apps/410320/manuals/EDF_manual_EN.pdf?t=1469006823

Steam group: http://steamcommunity.com/groups/EarthDefenseForth

Discord servers, some links may be temporary so cycle through:
https://discord.gg/vqXAs
https://discord.gg/a2tUA
https://discord.gg/CprNF
https://discord.gg/Zf4dKwC

Weapon chart with missions dropped: http://weapon.edf.jpn.com/4-1/
(You can switch to english via the dropdown menu)

FAQ:

"What missions are good for farming weapons?"
2 (Spreading Disaster) to get your basic gear for a difficulty, 14 (Preventing Landfall) if you can deal drones and Hectors, 26 (Crimson) if you can deal with shittons of red ants.

"Vehicles suck!"
Early levels of Air Raider vehicles like helicopters and mechs are slow as hell like their 2017 predecessors, but higher-level versions get much better response times and can be pretty useful, so stick with it and you can eventually cause some mayhem.

"The Fencer is slow as hell! I can barely move and aim with him!"
Learn to Dash Cancel: equip a shield and melee weapon as one of your weapon pairs and tap the Use Hand button for wherever the shield's loaded right as a dash ends and you can go again, though this will use some of the shield's durability. As for aiming speed, Fencer guns have heavy penalties to aim speed to offset their raw damage potential, so switch weapons if you have to turn/move quickly or use a mouse with dynamic DPI.

"What's the deal with VOIP in multiplayer?"
Microphones in MP are always transmitting and there's no option to control VOIP volume specifically, so use programs like Ventrilo or Discord instead. You can mute other players in the lobby by scrolling to their panel and activating it.

"Are any of the DLC guns worth getting?"
Nope, they get outclassed pretty quickly by stock weapons so save your money for mission DLC.