Hoo boy. So many tips, but I can't find the words for some of them.
First off, it's usually a horrible idea to go vertical if the enemy is right on your tail. If you go nose up, he'll follow, and while both are of you are bleeding airspeed, his guns will line up nicely with your fuselage. However, if you jink left and right a bit first, and pull up as soon as you think he's lost visual contact on you (hopefully he's neglecting his mouselook), you might be able to get the drop on him (In this situation, maybe try an Immelman Turn*). Finally, the 109 seems to perform better in the vertical plane than its competitors.
Next, be sure to vary your speed when necessary. If you go balls to wall the whole time, someone who lets off on his throttle a little might be able to get an advantage on you, be it out turning you or even "Slamming on the brakes" and "making [you] fly right by" (Right Maverick?). Even in a dogfight, if the enemy is behind you, try letting up on the throttle and engaging the airbrake. The enemy pilot might over shoot his mark, at which point you push the power back up and try secure your advantage.
Try to keep your altitude. The higher you are, the more options you have available to you. If you're high enough, you can try diving to the deck, hoping your opponent misjudges something and smashes into the sand, or you can try a Split-S** to quickly reverse your direction and confuse your opponent. Practice to find out the correct altitude where you can safely perform maneuvers. Also, the planes can perform extremely tight turns at the end of a high speed dive, so use that to your advantage (it's likely a side effect of the BF2 engine being built for jets instead of propeller-driven planes, but if you have to live with it, might as well use it to help you).
A quick tip: don't forget your rudder controls. If you bank left and rudder right, you will be able to maintain approximately the same altitude, depending on the angle of your roll. This way you can continue turn with your opponent without losing too much altitude. You can also use your rudder to assist in targeting. Because the airplane guns in FH2 don't have any convergence (yet :crosses fingers:), they fire directly straight ahead. If you're strafing a ground target and your guns are hitting directly left and right of the target, try sweeping them back and forth across the enemy by using your rudder. Also, if you're right behind an enemy plane and aren't doing as much damage as you think you should be, try adjusting your aim with the rudder. The best place to hit an enemy plane is the forward half of the fuselage (i.e the engine and cockpit). The wings and tail of the plane (or more correctly, their hit-boxes) are kind of wonky, especially in dogfights. The BeauFighter's wings (at least around the engines) seem to be ok to aim for, thoguh.
Finally, the Dicta Boelcke can be used even for FH2. Even though it was originally conceived for WW1 era dogfighting, it stills holds true. A more in-depth explanation can be found at
Wikipedia: Dicta Boelcke.
1: Try to secure advantages before attacking. If possible keep the sun behind you.
2: Always carry through an attack when you started it.
3: Fire only at close range and only when your opponent is properly in your sights.
4: Always keep your eye on your opponent and never let yourself be deceived by ruses.
5: In any form of attack it is essential to assail your opponent from behind.
6: If your opponent dives on you, do not try to evade his onslaught but fly to meet him.
7: When over the enemy's line never forget your own line of retreat.
8: For the Squadron: Attack on principle in groups of four or six. When the fight breaks up into a series of single combats take care that several do not go for one opponent.
Happy hunting and see you in the skies!
* Immelman Turn:
** Split-S: