Lots of factors can affect your odds of making the team.
Tryouts will be a little different at every school, and even between different coaches at the same school.
Your tryouts will probably begin with the coach trying to familiarize himself with who you and the other players are. This could be as simple as a roll call or as involved as formal introductions.
After that, there will likely be a warm-up led by returning players or the coach may have players warm-up on their own.
Once warm-ups are completed, the coach will probably test your conditioning and your soccer skills. How this is done, and what is focused on will be very different for each team. Some coaches may time or grade you on various drills. Other coaches may just have players scrimmage.
Whatever the case, you should have your best attitude towards the coach, other players, and your own skills.