It happens to me all the time. I'm at a bar or club or whatever and a guy will say that I'm really cool and wants to connect and asks me for my number. I give it to them.
Then after a few days, I message them asking what's up and how they're doing, they may respond but are clearly not interested in talking to me. Makes me feel really bad.
When and how do I message them to try to actually materialize a friendship?