What are the criteria for a good title?

A good title should come from what you've written. It's the last thing you do, once you've finished the thing. You can have what's known as a "working title" if you want, but your actual title needs to come out of the story. It also needs to tell a little bit about the story -- what's going on in the story, or who the characters are, or something interesting about the story. Here's a good link to look at.