Figured I'd make this thread as I've been playing a lot lately and have figured out why they call it Bad Company; Most people seem to be incredibly bad at the game. They don't seem to get the most basic concepts that are integral to a team based game like this.
Not that I'm a particularly good player, but none the less, here are 3 simple rules that have helped me (and as a result, the team I'm on) improve considerably.
1. You're not a L337 5n1p4h. Seriously, almost every game has way too many people playing recon, and they all suck at it as they think it's just a class for sniping. It's not, the Recon's main focus should be to spot enemies, cover objectives and call in Aunt Hillary (sorry, lame Wolf ET joke). Hate joining a squad to find I have 3 teammates just camping on the obvious sniper hill and dying every minute because their position and crap aim is so predictable.
2. Spot as often as possible, especially if you are sniping. All you have to do is press Select when you see an enemy. Being able to determine where enemies are gives your team a huge advantage, and if one of the enemies spotted is killed by a teammate, you get 20 points for a Spot Assist. Most games I've played as a Recon I've managed to get more points from spotting than from actually killing people (probably because I'm a crap shot

)
3. Swap kits. When a player dies, they drop their gear. If you're low on ammo, or find a kit that's more useful to the current situation than the one you're using, then don't be afraid to pick it up. This is especially useful when a Medic dies near you, just pick up his kit and revive him. He'll be swapped to whatever kit you had, but he's still more useful alive, and it gets your team a respawn ticket back. If you're low level then changing kits at every opportunity is a great option as it will allow you to use gear you may not have unlocked yet, likely resulting in you earning yourself more points as well as being more useful to your team.
I'm still a noob at this game though, so if anyone has some tips to share it'd be much appreciated.