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.

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. 

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.