Criteria for meeting another Litster IRL:
1) Being nearby (including nearby when traveling)
2) We should have chatted enough to believe we like one another
3) Believe that the other person is who she says she is
Those are certainly necessary conditions...they may even be generally sufficient!
I'd recommend a video-chat - makes it much harder to lie about (at least) their physical appearances. Many online use fake pictures to represent themselves, so that's one way to confirm they are who they say they are (physically, at least).