coin flips/all ins

For starters (without being situation specific) you're more often going to be reraising allin to the orig. shover... you want to isolate the ALLIN.

Many things to consider and each situation is very specific (too specific to give a generalized answer to).

Ok well first of all you dont know if its a coinflip untill you GET TO SEE his cards, but a lot of the time you get a general idea that theres a good chance there is. For example, you have ace king and you read some guy probably having a fair pocket pair. Now, usually you dont want to blow these away since other than what he contributes to the pot, there are the blinds and the bets of the other ppl that will fold to an all in, so theres a reason why you want to play them. But let say its a tourny, and your short stack... if you know your a good player, theres no point risking your game to a 50 50, even if theres more money in the pot, when you know you can probably get a lot more than that if you play good for a couple of hours, after all poker is a patience game. Good luck at the tables .