Begin your ACL survival plan by checking the weather forecast. If it is a hot and dry weekend, pack some extra wet naps and ice to cool yourself off with. A wet weekend and you may want to grab an extra umbrella.
Bring a small backpack for your survival kit. Include a handkerchief, wet naps, small umbrella, two bottles of water, small binoculars, a soft-sided cooler filled with ice and sunscreen. A change of clothes may come in handy for inadvertent spills.
Buy the three-day pass if you are traveling to see the show. Locals may prefer to get one-day passes in advance or buy tickets at the gate on the day of the show. Also pick up an ACL Fest guide at the front gate.
Bring a small folding chair. Some people bring blankets to sit on, but you will have a better view of the stage with a chair. Sitting also conserves much needed energy for the walks between the Austin City Limits Festival's stages.
Create a plan of attack with your friends. If you are going in a group, get together before the festival to plan which stages to hit throughout the day. The eight stages are fairly spread out, so plan on doing some hiking.
Beat the heat. If it is going to be a super hot day (and mid-September is hot in Austin), skip the early shows and arrive later in the afternoon. Austin City Limits Festival's gates open at 11:00 a.m. and shows last until 10:00 p.m., so it's a long day of music. Missing the hottest part of the day could be part of your survival plan.