1. Always keep opening your map to check for info, and for general direction (^^x0r), use the squad leader marker as well
2. If you're using an aircraft that has AIM-120 missiles keep them on so that you can scan the air at a longer range, most kills come from finding the target first, rather than letting the enemy aircraft come in and then reacting
3. Make sure you have enough distance between you and the enemy and that enemy aircraft isn't at a weird angle coming towards you, you can shoot them down from the front, they just need to be a bit further away - don't have an itchy trigger finger, just wait it out if you're not sure the missile will hit properly, you can always readjust
4. Lead your target when you are chasing them (bot jets have different flight models, they will always out-turn you, but brief windows of time when they are turning and you are on them are perfect to let off a burst of cannon rounds - even if it just gets them smoking)
5. AIM-9s are also viable as weapons, you just gotta wait for the lock (and pray no friendly AA is targeting the enemy) - some enemy jets don't even flare
6. When attacking Gophers or Stingers always pre-flare while your going to the target location - especially with jets like the F16
7. Make sure your sensitivity is good, and that you can rotate the aircraft with ease and less movement of the hand (if you fly with a mouse) - find what's most comfortable for you
8. If you have enemy jets on your ass just do what vanillapop said
9. Learn the AA positions, take them out in an order where they can't hit you all at once, coordinate with other pilots - quickly go in and out
10. If you miss the quad or there is something shooting at you, just dive and keep turning (I don't use the rudder here, it usually gets me out of danger), put as much terrain and obstacles between you and the thing shooting you
11. Compensate for bullet drop when firing at a longer range
It's all about practice in the end
This is what I tend to do, and I don't consider myself as good of a pilot as some of the people that I've seen fly on coop, hope it helps ya
(oh and don't listen to x0r, he's a hacker)