OK, here's an image that shows a couple important things I've found useful in AH...and they were apparently good in real life too. (The image is from an actual fighter training manual.)

EDIT: 5/28/08 - looks like the image I had linked got deleted. I'll see if I have it on my own hard drive.
Notice how the idealized firing pass is set up:
1. The attacker is NOT coming from dead astern. When you're directly behind the tail, you're looking at a SMALL target. The wings are slivers, and the fuselage is a circle instead of a cylinder. The only thing that's good about dead 6 is low deflection, but if he's climbing or diving slightly you can get fooled into missing anyway.
A little lateral separation, like this cartoon pilot has, means that you get a better view of his movement (which means better judge of how to lead him). You also get a MUCH bigger target to shoot at, and you're more likely to land damage. As an added benefit, you are setting up to extend past him with smaller risk of collision, and a nice chance to repeat the attack by yo-yo'ing back down at him from the other side.
2. The attacker is NOT coming from the same altitude. Added to the lateral separation, you get more of everything we just talked about. Better judgement of angle and velocity...better gunnery at an even bigger target...and more ACM options to continue the fight.
3. The attacker is pointed to the place he wants to shoot long before the enemy gets there. Guard against what some people call "gunsight ACM" -- moving the stick to keep the pipper on the target. That wastes lots of energy, since what you're TRYING to do is put BULLETS on him, not keep your prop pointed at him. Using gunsight ACM, you can't really think about the proper deflection until you feel you have tracked him well...and then you have to pull the stick AGAIN to get the shot set up.
Instead, learn to use the skills you already have from playing catch. A football toss involves everything gunnery does: You have to judge the speed of the reciever, the angle he's moving, and the speed of the ball before you fire off a pass. When you see him break, let your mind judge where he'll be when you get to firing range...and point your nose there NOW. Bingo -- you get a snap shot. When he's making a climbing bank like in the image above, point to where he'll be when your fining angle crosses his flight path, and let em rip in time for the bullets to be there first.
Now to make this work best, you should get an idea for how BIG the fighter is going to look in your windscreen at the distance you use for convergence. Don't rely on the icon data...get a mental image. (I jiggered around offline, filmed, and edited gun sight files to make a circle sight the same size as a P-51 at 300 for some of my favorite planes. You have to do it plane by plane because the program stretches the sight across the armor glass, which is different on different planes. )
4. And the image makes another REALLY good point that works great, even though I forget it too often. When ready for that final, full concentration firing pass, make a habit of doing a full 360 degree check for bad guys. The shot might start to look really good on purpose if the "target" is dragging for a buddy who knows his stuff!
See how that helps.