Also you have to know the plane itself in IL2,
like in category's and best situation.
the ME 109 (aka BF109)
is one of the best all round planes
the only downside is that its crappy behaviour on low speeds is fatal in a dogfight. so you have to maintain its high speed and try to take the enemy out by striking on him rather that try to fly on his six all the time and making too much turns which will highly reduce your speed.
Bi planes on the other hand, like the I-153 or the J8a and some others in IL2 are damn good dogfighters on low speeds and altitude.
no other plane can turn as fast as they can but your weakness is you cannot fly fast , you are easily shot to pieces when they have you in their gunsight.
but if you are playing it smart and a enemy fighter is engangine you try to evade his striking move quikly turn 180º right behind him and give him a good shot. als lure him to low altitudes as they sure will try to follow you and in that situation you have the upper hand.
also you got plane that you think are crap. when I first flew the TA-152 I thought...really how did the germans came up with this flying scrapmetal.
but when I red about it in my plane recognition manual (book) It stated this plane was used for high altitudes only. so I launched a quik mission with some B17's and P51 mustangs aroun 41,000 feet (13,000 meters) I noticed a big difference and creditted myself with 3 B17's and 1 P51 mustang before I ran out of ammo.
you also got the 2 engine fighters like the BF110, Beaufighter and the P38 that require a different type of tactic in taking out enemy planes.
these planes turn like fat cows so outturning a IJN ZERO for example is out of records. these planes need the Strike tactic . you have to track a fighter from above about his 6 O'clock. when you are close dive upon him keep your gunsight slighty in front when you are close like less then less the 1000 meters distance (with icons turned on 1.0 and below) wait till you have a good silhoute and you think its time to blaze hell upon him. I tried tis tactic multiple time and they prove to be very deadly for the enemy as 1 short burst of the heavy armament the P38 (which I used) straight upon the enemy turned the A6M2 zero into a flames and without 1 of its wings.
about gunnery in a level bomber like the HE111, B25 and JU88
you have to level your plane by using the level stabilizer (asign a key in the Control settings) and here is a very good instruction page of onboard guns of the B25
http://mission4today.com/index.php?name=Knowledge_Base&op=show&kid=240&page =5
hope this helps