Long distance shot
Use the sniper scope to zoom in on distant enemies,
then shoot them with the unguided rockets or cannon even without
a lock.
Surprise kill
Stay below a hilltop, hiding from enemies, rise up,
fire a few rounds, then dip back down to avoid return fire.
Saving missiles
Shoot fuel barrels and other explosive objects that
are next to targets with your cannon to get extra damage without
using missiles. Save your guided missiles for other helicopters.