In general (very general), the gap concept becomes very exaggerated on the bubble. This means you should be much more willing to raise all in (Read a few posts here, and you'll see that you should sometimes push with any two cards) than you should be to call an all in.

There's a program called Sit and Go Power Tools (SnGPT) by eastbay that uses ICM to tell you whether you should call/push in various situations (assuming you know your opponents' pushing/calling ranges). It comes with a tutorial that explains basic bubble play way better than I can--This part comes with the free version. I think it's linked to in the FAQ, but if not, you can google it.