When aiming, many people like to hold down the trigger and use the fully automatic option to try and hit enemy targets, don't do this. Use a quick burst, 2 or 3 shots, to try and hit your target. It reduces recoil and your scope will stay on target, you won't have to search after you're done shooting. Also, use the bipod when shooting a long range rifle. It reduces all up/down/left/right movement that happens when your character breathes.
When you're in the middle of a battle and need easy points fast, the Medic kit is the way to go. Throw one out in the middle of the playing field, and players will pickup health from 20 feet away giving you points. This works really well for low level players, and make's it easier to level up fast. Also, use the motion sensor in heavy fighting areas too. Each assist is 25 points.
Ok this is a easy way to earn easy xp. It may take some time, but it's something to do if you don't want to run around trying to shoot people. Ok you must equip the recon class with the mav. Now find a safe spot where enemies can't find you and harm you. Preferably the spawn. Now launch the mav and fly around and point the camera towards enemies and stay close to them until they get killed. When they get killed it gives you the spot bonus. And it's 5 spot bonuses for a spot ribbon. Those ribbons are worth 200 XP. So you can get 2000 XP by just flying around. And if you get really get good with it, you can try to aim for them and hit them with the mav, it will kill them.
Hey this is just a special hint on how to out tanks, just in case you like using the assault class and don't want to use the engineer's RPG/Smaw. So what you'll want to do is use the m320 which is the next unlock for the assault class after the defibrillator. The only downside is you're going to have to switch out your med kit to use it.
The m320 is a grenade launcher and holds up to 4 nades (with ammo specialist I think.. So just shoot at the tank with the m320 on the side or the back (where it's weakness is) and it usually disables the tank with 2-3 shots. Now if it's already damaged, that is good because you can easily destroy it. This is basically good with other land vehicles. Especially the buggies because it's disables it and kills the enemy. This is also better that an RPG and SMAW because it has faster reload.
Also remember to hide whenever you reload. You don't want to get shot out in the open.
In order to hold grenades in position before throwing them, press the throw grenade button, then straight away press and hold the fire button. It will then be held in place until you release fire and throw it.