When to shove and what to shove depends a lot on what your opponent will call you with. If he'll call you with any ace, then shoving with A2 is a bad idea, where QJ or 76 would be better because you're less likely to be dominated. If a "standard" raise will create a pot that is like 30-50+ percent of you remaining stack you might as well just shove because you're basically commiting yourself to the pot regardless of what cards come just by making the raise.