People who all knew each other seem more likely to go home if one or more of them gets sent back. It's rare for the last one to stay, but it's known to happen, especially if some of the others come back.

Then again there are cases like Portgas D. Ace, where he's been sent back seven times or something. Others have been here several years and barely left. Some people have never seen another from their world show up, and others get surrounded by them. It's no absolute, but there are a few tendencies. It's more likely that someone with a special power or familiarity with fighting shows up, but that's about it.