TIPS FOR HARRY POTTER PREMIERE! HELP!?

okay, now I have your attention; I was wondering if you have any tips for the harry potter premiere, for example what would be the best time to set off to ensure I'm at the front, what sort of things I could do to ensure I get an autograph etc. I didn't get to go last year, and this really is the last chance of meeting the whole cast of Harry Potter. Anything you suggest will be really great received, thank you :)