Depends how close you want to be. At the last show in Royal Oak (also general admission) I was in line around 6 I think when doors were at 730. I ended up being about 4-6 "rows" back, but my friend who showed up well after doors opened met me down there in the same spot without any problem (no pushing people out of the way to get the spot or anything, he just walked up). So basically, for me to get the spot I did, I wasted a lot of time in line.
I still recommend getting there pretty early however. Also make sure you pee beforehand, it can be difficult to fight for your spot back once you give it up.
And I would definitely be down for some chow before hand.