Fly low to the ground to go faster, but watch out for trees and other obstacles. It’s rare for the time you save to be worth the risk, but some missions have a tight time limit.
You can use your machine gun to shoot down many of the projectiles fired by enemies. It’s better to dodge, but if you can’t do that, open fire.
You don’t need to kill every enemy in most missions, so feel free to fly by anyone who isn’t blocking something you need to access.
Missiles and bombs have their own trajectories that you’ll need to get used to in order to use them effectively. Practice on early missions where time isn’t a big issue.
You can adjust the aim of your machine gun after you start firing, and it has a surprisingly wide range. You can use it to take out enemies from safe distances once you know what you’re doing.
While it’s tempting to go fast, you’re usually better off slowing down when things get hot. Enemies are pretty good at leading their shots, and slowing down will actually throw their aim a lot of the time.