Switching between the full cockpit view (F1) and the gun-sight-only
view (F4) will allow you to track enemy threats accurately on the GCI
gauge while still offering maximum forward visibility. The game's
clunky padlock view won't permit you to "check six" as efficiently as
the GCI gauge can, so toggle back to it regularly and keep hitting the
T key like a demon.
The huge blind spot behind your plane can be occupied by an enemy
fighter very quickly. It's best to keep wagging your plane back and
forth when chasing down an opponent because one of his wingmen may have
slotted into a perfect shooting position without your knowing about it.
Conserve your ammo! This is especially critical when flying the Heinkel
in the Spanish Civil War campaign because it will often take the entire
magazine to down a single enemy plane. (The damage modeling in the game
can be woefully off-target.)