My main question is while playing heads up, at what times is it better to
A) just call from the small blind with marginal hands due to the fact that you're getting at least 3:1 (even better with antes) and that you have the advantage of playing the rest of the hand in position.
B) play raise or fold from the small blind, basically pushing your chips based on ICM and the % that you're hand has going heads up against a random hand.
The way I've been playing it so far is that I play push or fold for sure if I'm below 10 BB, and mostly raise or fold between 10-20 BB.
The times that I'm less certain what to do is when I have more than 20BB and get dealt pretty bad cards... I want to call to see a flop in position, but at the same time it can lead to some bad situations post flop. I know it also greatly depends on my opponents postflop play, since I'm much happier to call in position against a weak opponent.
Anyways, I'd appreciate any advice from more experienced players/coaches as I'm just starting out 
