Most allied planes have rotary engines, which have no
throttle the engine is either off or on at full speed.
If you're flying for the Germans, use the throttle to
your advantage and change speeds often. (Red Baron II
lets humans adjust the throttle on rotary planes; however,
don't count on this advantage in multiplayer mode).
If an enemy flies across your nose, you generally don't want
to turn in the same direction (which is the novice pilot's
first instinct). Turn in the opposite direction and try to
get on his tail.
In heated dogfights, don't think two-dimensionally and turn
only horizontally (another tendency of novices). To keep
fighters off your tail, you should constantly climb and dive
as well as turn.