Don't drink to much is the best advice.
YMMV. I'm a happy drunk, so I have the most fun at shows when I've had too much to drink. LOL. Since I'm under random testing for work I can't do weed...so unbridled drinking is one of the reasons I love festivals. I don't have to worry about moderation and getting home afterwards, or dealing with my wife squawking that I drank too much at the show...she doesn't mind me drinking, it's of course all about getting home safely and not endangering others. I never have a problem sneaking in my brown liquor into the festy grounds. And the only challenge is getting my stuff packed after the music stops and getting back to camp without tripping over anything. I also have the collateral advantage of being drunk enough to sleep fairly soundly that night, which I rarely do at a music festival. LOL. Yeah I know it's not a good sleep when you're juiced up, but its sleep nevertheless.
I'll never forget that one time that I should NEVER have gotten behind the wheel after a show and coming home from the venue (not a festival). It was around 2am on either Friday or Saturday night and I was almost home. I peaked a hill and off in the distance like a half mile down the road I saw a random sobriety check point. It was only like 3 or 4 miles short of home. I've never been so panic stricken in my life, but somehow or another grace was shining down on me because I got waved through with only a driver license check. Never again.
Anyway, back to festy drinking...the biggest thing for me is to choose which night I'm gonna go big...usually Saturday night because Sunday music is usually kind of mellow. It gives me all day Sunday to recover for the drive back home either late Sunday or Monday morning. I don't like going big on Thursday or Friday and feeling like shit the next day...which is usually one of the best festival days, which is almost always Friday or Saturday.