Beer festivals are awesome. I realize that I'm responding to your post probably after the event, but here's how I try to roll with these.
Eat ahead of time. You'll want something in your stomach, first off. Eat enough in advance that you aren't still burping up your dinner while you are tasting brews. I try not to eat anything that leaves a "lasting impression" so to speak. I skip the pizza, tacos, and salmon and usually eat a good sandwich or a burger. If you don't eat ahead of time, you'll risk prowling the food carts and ruining your taste buds.
Have a bottle of water. Every beer festival I ever attended had bottled water available, but we bring one in just in case. It helps cleanse the pallet in between offerings, and you won't slip into the dehydration that beer can cause.
Bring a pen and a notebook. You'll taste some beers that you want to find again, trust me. And you won't remember what they're called... trust me again. So write them down, and write down the characteristics that you liked about them. You'll probably meet some folks that you want to meet again down the road, so you can get their social media info and such. Good for writing down phone numbers of beer supply places and breweries. And it doesn't hurt to snap a photo or two with your phone to remind you what you drank as well.
Start with the low IBU stuff to begin with. I looooovvve IPA's and have blasted through all of them right off the bat. It just served to kind of ruin the rest of the beers because I had this lingering hoppy bitterness the whole time. There'll probably be a list of the beers with the IBU's, specific gravity and so on. You can use it to plan your route through the offerings.
Bring a small pack of some sort. There's always stuff that breweries give away at these shindigs, and stuff they offer for sale.... glasses, shirts, Frisbees... and your pockets can fill up pretty fast, even if you wear pants with cargo pockets (I do, and recommend). Easy to carry your notebook, pen and water bottle as well. Sometimes the wife brings one of her larger purses, too.
Have a designated driver, or walk to the event, or stay in a hotel close, or take a Uber.... just don't drive. A beer festival is a blast; you'll meet great people, sample phenomenal beers, eat great pub fare, and basically have the time of your life... And a DWI will %&!!# the whole thing up.
Relax, have a blast. Beer people are some of the funnest, finest folk on this planet.