For nosing over, check to make sure the wheels spin freely. If the gear is wire, see if you can flex it forward to move the gear a bit more in front of the CG. Check your CG to see if it's not too far forward. Make sure you aren't starting in a pothole, or overly dense or tall grass if you fly from grass.

Beyond that, when you taxi, hold up elevator. When you start the take off run, start holding up elevator, then let off the elevator as the plane gets rolling and the nose-over danger goes away so you an avoid jumping off the ground too soon.