When you are only a few years older than the students that you are teaching, it is important that you do whatever you can to separate yourself from them. This might include acting nerdy, being unfriendly or even making yourself look older.
When I was starting out some of the students used to invite me to their parties on the weekends. I immediately decided to start wearing glasses instead of contact lenses to make myself look older.
Don't give your students the impression that you are peers. You are supposed to be the authority figure, no matter how old you are. This is especially difficult when you are a similar age as your students. Take every advantage you can get to look older and separate yourself from them.
Your students will be the ones who benefit.