Keep an eye on the weather forecast--you'll want to dress comfortably and bring the right gear, lest a rainstorm interrupts the day's headliner. Forecast.io (free; iOS, Android, Windows Phone 8, and BlackBerry) is a Web service optimized for mobile devices. Install the bookmarklet on your home screen to get an up-to-date forecast for the next seven days. Forecast.io shows what the weather will look like over the next hour, day, and week. You can watch a map with local weather patterns to see an overview.
Because festivals are all-day affairs, look into food options before you get there. I spent a fortune on food at Coachella--meals on the festival grounds and groceries at the festival campgrounds' general store were not wallet-friendly. If you're camping, bringing your own food is a good way to cut down on costs. (Just check the campground rules for what types of items can be brought in. Glass containers were a no-no, for example.) Coleman's Classic Camping Cookbook & Meal Planner (free, iOS) is a handy app to have for preparing campsite cuisine. Select recipes by cooking method (campfire, grill, none), type of meal, or available ingredients for yummy suggestions on things you can make yourself.
Not all festivals have camping options--many of them are in metropolitan areas where camping is close to impossible. Hotels can fill up fast if the festival brings in a lot of visitors, so if you find yourself stuck in a city with no place to sleep, Airbnb (free; iOS and Android) can help you out. I used Airbnb to find a place to stay during South by Southwest in Austin earlier this spring. Airbnb is a network of hosts who have opened part (or all) of their homes to travelers. You can browse the available listings, select a room to rent, and communicate with your host directly through the app.
Festival venues are massive, and when you add thousands of other festival-goers to the mix, it can be hard to find friends and organize a meeting spot.
While you should always be wary of using location-aware services that broadcast where you are, they can be helpful in noisy situations where cell service is jammed. For iPhone users, there's Find My Friends, but for a more-inclusive offering, try Ban.jo (free; iOS and Android). Not only can you search for friends' exact locations on Ban.jo or get a notification when friends are nearby, you can search other activity nearby. Ban.jo collects posts from a variety of social networks and curates them based on location, so you can make sure you're not missing out on any of the action going on at other stages or tents.
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