It depends a little on how I think he sees me and how far to the aggressive end of the spectrum I see him, but I think I would most often check raise the flop in a NL tourney. I would want to get my chips in the middle if I thought him capable of playing Ax and calling an all-in.

In limit, I would bet the flop, and consider check-raising the turn if he flat called the flop.

In both cases I would be kicking myself for flat calling preflop.