I think the way you tell whether or not people are sincere about wanting to get together or hear from you is their follow through! If someone says 'let's get together sometime' and you suggest a specific time and place, but hear nothing in return... then I would give them 2 chances and then move on to the next person. If they change their mind or their circumstances change, they can contact you.

I think you have to kiss a lot of frogs to find friends you click with. On another message board I am on, someone said that she has four misses for every 1 hit friendshipwise, which sounds about right to me.

I would really not take these things personally, if possible. Sometimes the timing is just wrong. A potential new friend emailed me a couple of weeks ago about getting together and I still have not gotten back to her because I've been too busy -- and now I am embarrassed that it took so long, which makes it even harder to contact her!!