A question about bubble play

I was just wondering... Most of the better players on this forum know when pushing is +EV, because that's basically what it takes to win, at the lower buy-ins at least. Raptor plays 20 tables, and probably makes 3 bubble decisions every second, and I bet most of his decisions are good, too. [img]/images/graemlins/smile.gif[/img]

But I have been playing SNG's for a few weeks (or maybe months) now, I have bought SNG Power Tools, and still I very often find myself in situations where I don't know if going all-in is +EV or not.

Sometimes it's obvious, when you get AJs on the button shortstacked, but what if you get Qxs UTG with a short stack? (just an example) I usually have to check first. Most of the time, it's pretty close. When I check how I did after a tourny, I sometimes am surprised about what SNG PT says about some hands too.

So my question is: if you almost always know when a push is +EV, how do you know? Have all good players experimented with SNG Power Tools until they understood exactly how it works, and know what to do in each situation? Are they all mathematical geniuses? Or is it just experience? Because it's very hard to learn what is +EV and what's not by experience, especially when it's close, me thinks. [img]/images/graemlins/tongue.gif[/img]

Then one more question: it's very important to know call ranges if you want to calculate EV. How do you decide what everybody's call range is? You usually find out too late. [img]/images/graemlins/smile.gif[/img]