Go out, talk to people, repeat. You have to learn that a rejection is no big deal. The cliche questions are fine to get started. What is your name, how is your day, what do you do? If they answer with anything more than 1 word answers then they are also interested in talking. Two of Dale Carnegies best items of advice: 1) Remember their name and 2) let them do the talking. Listen and ask a question, listen and ask a question. It is very true that the person who does the most talking in a conversation will typically feel like it was a good interaction.

I was once very shy, and decided to change. It took work, but people I know today think I am the most outgoing person they know. They simply do not believe I used to be terrified to talk to other people. I also used to think no one liked me. It just so happened the vibe I gave off was to stay away because of my shyness.