I'm in the 'hold nearish the nose and hang down' camp rather than the 'put foot on board and push up' brigade. I've tried the latter but found I was affected by the force of the wave more and couldnt get the nose as deep.
for big waves (where you want the nose as deep as possible) I do lift myself up a bit above the water and then drop in from a height, just to get deeper. but usually just from pushing up with my arms rather than getting on a knee
a bit of wax on the rails where you grip them to turtle roll is a big help.