This is my ritual for all open taping gigs:
In the parking lot, I'll make sure I have everything I need, and make sure it all makes it into the bag that I'm using for the night. Then I'll put my ticket in an easy to access pocket, and head for the main gate, or gate 1. More often than not, the main gate is the area where a head of security or other person in the know will be located if the kids at the gate take issue with your gear. When approaching the gate, I'll take my bags off of my shoulders, and start to open all of the compartments of my bag so that security can look inside and inspect the goods. I'll walk up to the person in charge and just say "It's all audio only, no video, no cameras", which is what they want to hear. This is sort of a weak version of the Jedi Mind Trick ("These aren't the droids you're looking for), as it gets security on your side right away. If you have pockets zipped up or stuff looking hidden in the bag, the Jedi Mind Trick will not be as effective. Now, 9 times out of 10, this will be sufficient, security will not often wand or pat down a taper, figuring any contraband you have on you will be in the bag, so if you're looking to sneak something in, it's almost as safe in your pockets as anywhere else on your person. Unofficially, of course, but I'm just telling you what I've seen. So you're past the inspection, security will then pass you along to the person that scans or tears your ticket, and you're in.
For DMB and other "tape from your seat" artists, your best bet is to keep the legs of the tripod folded up and stand up your stand between your seats (assuming you have two seats next to each other), and lash the hell out of the legs with duct tape until that thing isn't going anywhere. You'll still have to guard it during the set, because every drunk motherfucker in the place will think your shiny aluminum stand makes the perfect drunk crutch while heading to the bathroom - I'm just warning you ahead of time because this will happen, and at a DMB show, often. Offer your hand and forearm to keep them from grabbing the stand, and keep your cool because security is already watching you. Trust me, nobody working security in the venue has a clue, but they'll let you keep running as long as you don't cause any trouble to the people around you, and you're not in the way of the crew working the gig. I usually stand for the whole gig and leave my bag in my seat so it's mostly safe from spilled beer and getting stepped on, etc. I did have one drunk bitch lean over, falling onto my bag and turning off the power on my UA5, but at least nothing was broken. Just be prepared for anything.
Any other questions about taping at big shows, or taping DMB in particular, shoot me an IM. I haven't been to a DMB gig in a while, but I've taped other 30 DMB shows or so.