Early player, Low M all-in. When to isolate?

You are in the middle/late stages of your tournament. A player who is desperate and needs to make a stand does so, going allin for about ~3x(BB+SB). You are seated after him while there are N players yet to act of variable skill, but no idiots. Your stack is big enough that calling and losing will not break you. You have at least a good enough hand to look him up.

Question: For what range of hands, in what range of circumstances, do you chose to isolate yourself with him, rather than call.

This question is general to a fault, so chose as you wish any variables unspecified.

I don't really find myself isolating very often in SNGs, anyone else feel this way?

Early on, when there are a good number of players left (at the table, not necc. to act), and when I have to risk a fairly large amount to isolate, then I'm either raising for value rather than to isolate, or I'm not looking him up at all.

Closer to the money, I sometimes don't mind if someone else calls and we check it down to bust him. It depends heavily on the situation there, though. I will definitely isolate if I'm afraid a big stack further down will see my call as weak and come over the top to isolate himself.