When it is back to back to back waves, and they are up to head-high, I think it is time to find another activity... I will be curious to read what others say, but my best tips are (sorry if they are obvious):
1. If there is time, standup, paddle as fast as you can, and then either dive over or under the wave the wave depending on size (yep, the leggie will be punished) - you can also do this while kneeling, but still dive over/under the wave
2. As above except flip the board over the wave towards 2 o'clock while you either fall backwards towards 7 o'clock or dive towards 10 o'clock - i.e. out of the way of the board if it comes back with the wave
3. If the period is very short, and the wave isn't too big, hold one hand on the kickpad while you dip under the wave backwards - so you don't waste time retrieving the board after the wave
4. If they aren't too big, prone paddle with the blade of the paddle under your chest. You can't properly duckdive but its better than nothing.
A couple of don't-dos:
1. Don't try to go through on your knees - you will get whacked (in the guts by the wave or in the face by your board) and pushed back faster.
2. Don't hold on to the leg rope - people have lost fingers
Having said all that, right now I have a 15+ knot on-shore with messy surf - and I am here on my computer...