Allies

As the Allies, you should watch from which airfields enemy interceptors are launching, then bomb and fighter-sweep those fields the next day to pound the enemy fighters on the ground.

Axis

As the Axis, do not overcommit to the first raid that you pick up, because it can often be a feint. Plot your intercepts to harass a bomber stream over the length of its route, instead of doing one large cluster attack, which leaves you without any follow-up ability for quite some time.

Escorts

As far as fighter combat goes, escorts should always have at least one group flying high cover at 3,000 to 5,000 feet above the main group, and interceptors should be set to take this high cover into account.