I would think the tip most relevant to your game style is that you must be standing behind your opponent when you use the knife in order to remove his dog tags!
BF3 is intolerant of other programs running in the background so ensure you shut down all non-essentials and, if you have your anti-virus/ security program set to auto-update, alter its settings so it will not fire up during the game (or your game will probably crash/freeze up). It should not be necessary to shut down AV or firewall and thus expose your PC to security threats - resist any temptation to do so.
If you are running a 32-bit system and find that the game does freeze or maps don't load up as required (i.e. you are left staring at the battle log screen and a pop-up saying "loading level"), do not panic. There is a simple fix to make more memory available to the game.
If you're interested in learning to fly the jets and choppers, log on at a time when the server/s have few people in them and don't worry about your score. Spawn into a chopper and experiment (going up and down and keeping the thing level is a good start, then tilt the nose down a little to go forward - you'll soon get the hang of it. You could even ask Damit not to shoot you down whilst you're in "flight school"!
Most of all, don't get disheartened in the early days. You will be shot frequently and, if such things matter to you, your kdr will not look that good. There are many ways to contribute to your squad without having to be a crack shot. Some intelligently placed land mines can stop/slow the enemy assault, first aid packs are always welcome after a fire fight and we all always need ammo, so try playing as engineer, assault/medic and support. If your squad lacks any of these, it'll aid it and make it more balanced if you choose the missing class.
(I always fire up Teamspeak after Origin and BF3. Use TS when playing!)
See you on the battlefield, soldier!
Oh, and don't mind me... I always play like an idiot!
I think I learned how to fly the chopper DeeJay.