Without any documentation, I suggest you fly your sim heli in a manner as close to the real thing as possible. I mean, you have seen real helicopters fly, right? So emulate them on the sim. No sudden drop or gaining of altitude, no abrupt turns, etc.

One tip:
When starting to do forward flight, try to maintain constant altitude as an exericse. You can do this by decreasing throttle/pitch a little bit. Experiment on the sim. Without varying your throttle/pitch, your heli will gain altitude in forward flight.