This stage has to be played, according on your stacks and position, not that much about the preflop choice of playing cards.
Everyone will be agreed that you have to stay tight till the prize places, but in some situations you have to take a different choices.
You are middle stack, just from this information you have to know that playing versus big stacks is a big mistake in the most of situations. You have to hunt the exhausted players, small stacks and holding the place at all price!
Stealing the blinds is good too, ive read about it, but do it rarely. That is good when you are the big stack, the idea is to steal the blinds with all in or huge raise, cause the blinds are big at this stage of the tournament. Its risky, but alot of players are playing that way, probably cause the small stacks are protecting their chips till the bubble ends.
At all, the specific situation, have to be played by specific way. You just have to learn, practice and will be easy to know what is the better choice.