How to not be shy in high school?

I started high school a couple of months ago at a new high school and I was just wondering how to not be so shy. People don't like that me that much because I can not open myself up to let them see the real me. I have had never had any problems with having friends once people get to know me it is just that it feels so awkward when talking to most people because I have no idea what they are lke much less what to talk about with them. Please help me.