Hu5ky,
Are you controlling your pitch and yaw with a joystick or the keyboard? Regardless of which, some things to keep in mind are:
1) Fine adjustments will benefit you in the long run. The heli will tend to respond better (since flying in 3rd person prevents you from really getting scope of how exactly your chopper is oriented, thus preventing you from making 10-20 micro-adjustments in the span of 15 seconds.
2) Speed isn't your friend. If you're coming into a LZ, for the sake of your life don't come in HOT. Plan out your landing about 1.5km out, have your speed reduced to 50km/h by like 600-800m and start getting to that point to where you're almost at a standstill as you're descending to your target.
3) Flying in 1st person is difficult because you can't see targets on the ground easily, it does however provide you with a good idea of how you are oriented at any time. Flying 3rd person is fantastic for target acquisition and figuring out where you're going next by ways of landmarks/clear areas to land. Both have their benefits and drawbacks.
4) Some helicopters handle great and of course there are some that fly like a turd on a stick. Taru's are very nimble and agile (believe it or not) whereas the Huron can be a little more pesky in its turning. Sometimes a chopper will react to the physics of Arma and do some funny stuff like doing a 180 turn as you are pitched backwards (flying backward). Single cockpit choppers can be quite nimble and fast but its easy to get shot out of said cockpit.
I've probably left something out and haven't even touched on attack choppers but I hope this helps a little. One good thing to invest in when you Kit out is the Spec Ops Mask so that you have Night vision, and infra red that can help you decipher threats/targets from a good distance away while at altitude in a pinch.