Unfortunatly, CFS 3 has a lousy 'help' and the suport on the oficial site is almost non-existant.

CFS 3 should have a training school like FS series. Real pilots practice before flying for real. The training missions are unsuficient.

For instance I found that assigning all my wingmans to atack a single ground target is a waste of bombs. Also, when they dont have bombs left and can only straff targets with rockets or canons, make shure you get a good visual on the target you are trying to fry.

For instance, atacking dug-in infantry/artilery or factories/shipyards dont choose the 'building' target because these targets are spread in a relatively large area and your wingmans will aim for the center of the target over shooting the same empty area over and over. Select vehicules that are in the target area and assign each pair of wingman to atack them. That way you will be shure that the whole target area is atacked.

Dont rush your return to base. Save some machine gun and canon ammo and assign wingmans to do the dirty ground target strafing unless they fail you have to do it yourself. If you really dont find any thing fun to shoot at (Messerchmits eh eh eh), spend your amo before returning on easy ground targets like vehicules.

Study the map before flying. Check for factories near the target sector and their positioning relatively to the goal target.. 4 wingmans droping 2x4 1000lbs bombs is more than suficiant to wipe out any goal target (except ships formations). After you completed the goals, head for the sector factory and burn it to ruble.
If you are looking for air targets (ex fighter sweeps) there are always more enemy aircraft in the area so dont worry if your wingmans shoot all the goal planes and have all the fun. Go for enemy airbases areas. I always find Fock Wolve formations and these are easy preys.

Make shure that when you get the chance to shoot it down... shoot it down! Inspired by my CFS 2 tactics I always saved alot of ammo and used only the required to bring a target down. Unfortunatly, in CFS3, with realistics setings in Hard, planes are much more harder to shoot down and kills arent confirmed if they hapen without your being arround. In CFS 2, after warping to base you would get reports that that Junker you shot 2 hours ago fell 90 miles away. Here you dont.
And there is nothing more anoying then having a black smoking messerchmit on your sight, your work of dog fighting art, being shot down by others with only a small burst while you were waiting to him fall on his own.

Just a few tips of my own, share yours! 

First of all, Practice in Quick Combat ,thats what it is there for.

Second of all, there are way too many different tactics, it depends on the specifics of the situation ,your question is too broad.  Be more specific and I will help.

Some thing I learned yesterday. When atacking ground targets far off into enemy lines you are most likely to meet air bandits on your way to the target. Unfortunatly you will most likely be carrying heavy ordnance to strike the ground target, and dogfighting becomes a risky decision. Still you will notice that Spitfires cover you aldo they take longer to shoot down the enemies than your wingmen would.
Whatever you do, dont assign your wingman to air targets because they will jettison their weapon load. Instead spread formation alot and shoot them down yourself. The spitfires will most likely take care of most of them. Then when reaching the ground facility target you will have all your 7 wingman fully loaded with bombs 

1)assign ur wingmen to enemy aircraft end let them soften targets then call them into formation. shoot down down enemy urself  than (it is vital for me when engaging devastating bombers)
2)dont fire until u saw enemies name, get close than needed
3)u can take mk108 or mk103 ordnance for extra bullets
4) u can arm rockets in CAP missions and fire them before u free up ur wingmen
5)know that ai will not black-out or grey-out (?) in dogfight , gain altitude an do nonsense maneuvers when outnumbered in dogfight especially,
6) u dont have to FOLLOW target cone. it shows where the enemy is , not where he will be soon
7)hadle gently, breath deep
8)sorry for my english