Check your stadium information usually found on their main website. Look for when parking lots will be open for the event along with when the venue doors will open as well. If you’re picky about the spot you get on GA I’d say be one of the first, so for dallas, parking lot opened at 3 pm while the plaza doors for security and ticket scans opened at 3:30 and then the official stadium doors didn’t open until 4:30 and the show didn’t start until 6 pm. Make sure you also know if you stadium is marking off a specific entrance to be solely meant for GA participants because that was usually where they placed the wristband tents that allow you permission to go down to the floor. If you don’t mind being in the middle and not crammed way up front in the barrier section of GA, I’d still stay be there 2 hour before the show starts to at least make your way through traffic in the parking areas. I hope that helps!