Without knowing any variables, it's so hard to answer your questions. But just answering them as asked, I would say it depends on the situation I'm in. And knowing nothing, if it's a choice between all in or pretending you have nothing, I'd chose all in. Everyone may fold, and you get very little, but if not, at least you're getting it all in with the best starting hand you can have. And that's even assuming you mean go all in or pretend you have nothing, pre flop vs post flop. When you get a chance, try posting some specifics of a hand you were in, and how you played it, and ask what could have been done differently. I bet you'll get some feedback.