If you want to go and do things and see people, arrive about 8am~11am. Panels start at 8am, and Main Events start at 10am. First day, official start is usually around 10am when Opening Ceremonies is - and usually nothing is before that. This includes the artist and dealer halls, they only open once Opening Ceremonies has begun.
I'm an early-bird and am up walking around at 6am and the place usually only has around 100 people milling around outside of staff until 9am; unless you want to talk about the Registration lines, for they are their own monster.