Try and be pretty consistent in your positioning of the aircraft so that you're in the same place every time you get to 50 feet above the threshold, i.e. rate of descent, speed, lateral positioning should all be correct. A good landing tends to follow from a good approach, if one day you're doing -400 fpm over the threshold and the next -800fpm due to your positioning relative to the ideal profile then it's going to make the judgement of the flare more difficult, especially when you're new to type.
The biggest problem I see is people chasing the "glide" at low level, especially in the last couple of hundred feet, and effectively de-stabilising the approach to a certain extent. Don't chase the PAPI's at low level ( below a couple of hundred feet ) you should be going for your aiming point on the runway. Accept what you've got at 50 feet, look down towards ( but not at ) the end of the runway and start a gentle flare at about 25/30ft assuming you've been at a sensible 700 ish fpm. Smoothly take the power off almost simultaneously and keep that gentle descent rate till you touch.
And don't worry about the odd cruncher, we all do them from time to time!
WBV