1. Use the zoom key
2. Use F3 and your various gun positions to keep an eye on your surroundings. Do this even if you are in formation with other bombers/fighters. Too often, even with an escort, once there are a few cons in the area or the other bombers are all glued to the bombsight, bandits can slip in and slice a wing or engine before you even know what is going on.
3. Learning to lead properly is like using the force, you'll know it once you've got it. Watch for the flashes on the enemy, that means you are getting hits. Watch WHERE the flashes are landing, getting hits is better than not getting hits, however learning how and where to place your weight of fire is the difference between getting a kill and getting a kill and losing a drone.
4. Know your enemies. This is especially important when you have an entire gaggle queuing up like 12 year old girls at a Twilight sneak preview. Prioritize your targets based upon threat level. The more cannons, the higher the danger. If you have multiple bandits incoming, give the wing mounted .50 jockeys a love tap spray to the canopy or wing root if they are closing faster than the cannon boys, then concentrate fire on cannoneers as they get in range. 262s, 163s, 190s, 152s, 109s, and P38s are top priority. Spits and Hurris can be very bad news as well, but only if they know what they are doing. A newb with centerline mounted cannons can hit a buff pretty easily.
5. Unless you are trying to ward them off, don't stop firing. This is followed with the caveat that you only fire when you are going to hit them. With rate of closure being what it is, use every millisecond of time that your firing window is open to thrash hammer them.
6. Don't chase kills. Your sole mission is to deliver those eggs with precision and then land your sortie. Unless you are trying to bait enemies away from C-47s or otherwise pulling pressure off someone else, just keep flying. If I smoke an enemy fighter, depending on the mission leg, remaining ammo, number of friendlies in the area, once he breaks off I will stop firing. If one of your teammates gets the kill, take pride in setting it up and doing your job.
7. If I am alone (say strat-bombing, or trying to disable a base supporting an attack elsewhere), I will watch (especially an enemy climbing up on my 6) very closely. As they are often wondering whether or not you even know if they are coming, I will let them wonder as long as possible. I will wait until either A) they start firing or B) they get within optimum range before letting them have it. With guns converging at 500, gauge their rate of closure and open up on them ~550 or 600. If they are creeping up to get within knife range, they will most likely not even get a chance to fire.
8. You can slice a wing (or wing tip) off of an enemy fighter with relative ease (not so much with American Iron, but definitely the Loofawaffles and Shpitz). This is an easy way to abruptly alter an enemy pilots plans, but in some situations this can also guarantee a collision. A fighter screaming in on a slashing attack, or coming in high 3/9 for a cockpit line-up will spin right through your formation if you slice a wing. This is less than optimal.
9. Don't waste your waists! (Keke.) While almost never as useful as your primary gun positions, taking any shots you possibly can with your waist guns saves valuable ammo in your turrets. Nothing is worse than being a sector away from landing those strat bombing points and staring at 0's in your ammo reserves whilst staring at Zero's on your tail. (ZOMGEE THE COMEDIES!)