2nd year as a "pro" although I've never taken advantage of the preview night. As big a spectacle as it is, and as many things they have going on, I find 2-3 days is plenty.

As far as tips go, just know that shit is going to be crowded everywhere, but especially around the video game and movie areas. Ironically, the comics areas are the lease densely populated and relatively easy to navigate through. If you want to see the movie related stuff, it's best to make a b-line towards it soon as the doors open, because the bottlenecks are only gonna get worse as the day progresses.

Wear comfortable shoes because you're on your feet all day accumulating free shit which starts weighing you down pretty quickly. Actually, you know what, that's my tip - Try and curb your lust for free shit. Ultimately most of it is just shiny garbage that you'll never find any use for. Comic Con is kind of like Mardi Gras with the plastic beads. They hold no value whatsoever, but get enough people together at the right time of year in the right town and suddenly they're a form of currency.

Also, bring a backpack and toss some granola bars in there or something. Plenty of great food available outside the con, but if you're stuck on the floor you don't want to be at the mercy of the pretzel stand.

I dunno what your work obligations are, though. Are you going to be working a booth all weekend? If you do have free time I'd suggest you look over the SDCC schedule a week ahead of time and map out any panels you wanna hit. If you try to figure that stuff out while you're right there in the mix, you're going to miss something.

PS Please bathe.