Personally I almost never do. If the dealer is kicking butt and getting 21 over and over then sure. But it's time to find another table at that point anyway. Now hears the deal you never insure a crummy hand. If you've got a 3-7 (total hand amount) or 12-17 ( total hand amount) don't bother insuring cuz your probably going to loose against his ace anyway. If your showing 8-9-or10 you've got a good shot at 18-19-20 so it's up to you. If you got 11 that's your double down no matter what the dealer is showing. Personally that is the only time I would insure. 11 is your best hand ALWAYS double you will win more often than not. Good luck!!