Join a club; backpack travel; get a job handing out fliers; say hello to everyone you walk past. Just do it. Repeatedly. Don't judge yourself after each encounter. Instantly drop any negative feelings and move on to the next encounter.

My big epiphany was that my shyness was costing me way too much. It's uncomfortable to think about the friends and opportunities I let go because I was too shy. Never again. I'd rather look stupid to most for the sake of the few that understand me.