Leave HOURS earlier than you think you need to. I went to a McCain/Palin rally in Virginia Beach, left my house 4 hours before the event began (30 minute drive) and arrived two minutes before the start time, standing so far back I couldn't see the stage, and could BARELY see the overhead screen. I had to use far-away overflow parking and stand in the longest line I've ever seen. (remember security - pack light)
I encountered a few amazingly ballsy women who just pushed in front of people for a better spot, and one really annoying guy who insisted on clapping with his hands raised high above his head, blocking my view of anything.
Other than that, it was a great event, even if I only could HEAR it. Have fun!