Press [ Q ] to draw and holster your weapon.
[ Left Click ] or press [ Left Mouse Button ] to fire your weapon. Weapons have unlimited ammunition, but generate heat when fired. Your weapons heat level is displayed in the lower left of the screen. Fire in short bursts to avoid overheating. If your weapon overheats, it will not be able to fire again until the heat dissipates fully.
The Sabotage Power makes weapons more likely to overheat. Some enemies can use Sabotage against you!
When an enemy gets too close, pressing [ Left Mouse Button ] will initiate a pistol whip or rifle butt melee attack. This will cause some injury, and may force enemies back or knock them down, giving you a chance to shoot them.
Press [ Right Mouse Button ] to toggle in and out of targeting zoom mode. While zoomed in, your weapons fire will be more accurate. Sniper Rifles are very difficult to use if not zoomed in.
Press [ F ] to use your squad's First Aid Power. First Aid heals everyone in the squad, but consumes 1 medi-gel per use, and has a cooldown period before it can be re-used.
Training in the First Aid Talent improves the amount of health restored per use, and the Medicine Talent reduces the cooldown time between uses. The combined skills of ALL squad members with these Talents will benefit your squad.
Press [ R ] to throw a grenade. You can carry a limited number, so use them carefully. Grenades "stick" where they impact and can be remote-detonated by pressing [ R ] a second time. This makes them useful as traps.