Okay, I think I'm becoming more of a rotor head every second.
Okay, here are my tips.
1. Don't grip the stick like it needs to be strangled. I use a light touch.
2. I have the realism set as high as it can go. With no Null Zone on any axis and throttle. I got that tip from Hovercontrol.com, I always keep realism on high so I don't know how it reacts with it low.
3. My guess is that you are trying to come to a hover, and the helicopter starts drifting in every which direction. For me, I always tried to adjust the attitude to what I figured was normal and my heli would drift backwards, whip around and then lose directional control. Try to keep some forward speed. The helicopter is much more controllable in forward flight with less corrections. Keeping the chopper moving forward at 1-2 kts is much easier to control than if you try to maintain a hover at 20 feet AGL and try to land vertically.
4. Use the VC! ! ! I can't stress this enough. It's there for a reason. It is possible to use the 2-D cockpit, but it is also to drive a car blind folded while trying to play the piano from the passenger seat. It just isn't easy.
5. Minor corrections. I am/was a very ham-handed simmer. Even flying in real life, I prefer quick sharp banks and rolls than slow and smooth. You don't need to jerk the stick forward or back very hard. I realized that I don't move the stick very much when I play because it just doesn't need the amount of "convincing" that fixed wings do. I also use a little-bit-forward-back-to-neutral approach as well. I don't just hold the stick forward or back, I ease it forward a sec and bring it back. Ease it forward a second and then back to neutral. Almost like you are trying to touch an imaginary wall of molten lava in front of the stick. It kinda looks like you are shaking the stick slowly. That way, if the helicopter seems to start getting away from you, you already have the stick in a neutral position and takes equally minor control input to bring back to equilibrium.
I hope this helps. I've only been flying the FSX choppers for a few weeks but now I'm hooked.
If you want an awesome add-on, the Bell 412 from
http://www.Hovercontrol.com is the best I've seen so far.