Step 7: Like a Boss
Walk up to the rent-a-cop like a boss. Chat with him or her, looking them in the eye and being cordial. After all, this kind person is going to save you $60 on booze, remember? They're part of the game. Open your cooler for them - offer them a sandwich! Why not?
The last place they're going to want to look is underneath your cooler, and even if they did, it will take the trained eye of someone making more than $12/hr to see the seal now that you've gently scuffed the bottom up a bit on the walk to the gates.
Find you and your friends a spot to set up camp. Get out your chairs and blankets and sunblock. Get comfy, you're going to be there all day.
...and when the mood strikes, get a friend to help you lift the cooler up and have another person use a car key to pop the bottom open. Your cooler will pay out like a slot machine and everyone sitting around you will probably get a lot friendlier. But hey, you have a whole handle to drink, what's the rush?