I really need to know how to talk to people without acting awkward

Today I was at a summer school and it was very awkward during break and lunch since I had to sit alone. My other friends either didn't sign up or are on vacation and will start summer school in a while. The people I tried to sit with it just felt like they didn't want me to sit with them and ignored me when I tried to talk to them. I also tried to talk with someone I found cool but I didn't know how to talk to new people so they probably ended up thinking that I was weird. All the other students here are really intimidating for me to talk to since I don't know if they're nice or if they would be mean to me. I don't want to sit alone anymore.