I realize that this is kind of long, but take a few minutes to read through this. Show interst in the person you are talking to. Conversation includes being a good listener. Ask open ended questions that give room for explaination. Closed ended questions that bring about one word answers are conversation killers.
People like to talk about themselves and like to have others show interest.
We all have this. Remember, being rejected by someone that doesn't know you means nothing. It is merely a reflection of what the other person is feeling at the time or perceives is right for them. Maybe you remind them of someone else. It may be something else in their lives at the moment that has nothing to do with you.