It happens to all of us, eventually: an iPad app you're using freezes up, or it takes too long to respond. Although Apple's mantra "it just works" is true most of the time, sometimes things just don't work. Fortunately, there are a couple of pretty easy ways to deal with apps gone wild.
Option #1: Quitting an App. The first (and easiest) thing to try is simply stopping the app that's giving you problems. First, pull up your task bar by going to your home screen, then pressing the home button twice. Just press down on the misbehaving app until it starts jiggling, then press the red minus sign in the upper left. Confirm that you want to close the app, and poof! It's gone. Now try to restart the app. In most cases, this will solve the problem.
Option #2: Reinstalling the App. In those cases where it doesn't work, reinstalling the app is the next thing to try. To do that, press down on the app icon (not on the task bar, in the regular place where it lives). Then press the black x in the upper left corner. Confirm that you want to delete the app, and it will be removed from your iPad.
(Warning: some apps store data in them, and if you delete them you might lose all the data contained in the app. Before deleting an app, make sure the data is backed up somewhere else, or that you don't need any data in the app.)
Next, go to the App Store and press Purchased, to see those apps you already own. At the top of that screen, make sure Not On This iPad is pressed, so you can see a list of those apps that aren't currently installed on the device. Navigate to the app you just deleted, and press the cloud icon to the right of it. After you enter your iTunes credentials the app will be reinstalled.
Option #3: Reboot! If this doesn't solve the problem, or your issue is much worse than a single app, then rebooting the iPad might do the trick. You've probably done this before: just press and hold on the sleep/wake button for three second, and slide the button on the screen to power it off. Once it turns off, press the sleep/wake button again, and it will turn back on.
Sometimes this doesn't work - the iPad is so frozen up that pressing the sleep/wake button has no effect. If that's the case, the press and hold the sleep/wake button and the home button at the same time for 10 seconds. This will perform a "hard reset" on your iPad, which is basically the same as a reboot.
The Nuclear Option. If all else fails, you may need to wipe the device and start over. There are two ways to do this, depending on whether you're using Apple's iCloud service.
First, make sure your iPad is backed up. You may be using the iCloud service to back up your iPad, or still using iTunes. Either way, do a backup (if your iPad is in crisis, I hope you did a backup recently!). Then take a deep breath and head to Settings, then General, then Reset. Press Erase All Content and Settings. This will return your iPad to its original factory settings, without any of your content on it. The iPad is basically a new device for you now, and starts with a Welcome screen; after you choose your preferred language and agreeing to the Legal Terms, you'll get a screen that gives you three options:
- Set up as a New iPad
- Restore from iCloud Backup
- Restore from iTunes Backup
If you're using iCloud, select that option. You must be connected to a wireless network for this to work, and you'll be prompted to select a nearby network. You'll be prompted to sign into your iCloud account, and you'll then select the backup you want to restore. iCloud will then restore all of your settings, and reinstall all of your apps. If you have music or videos on your iPad you didn't get from the iTunes store, you may need to transfer them manually from their source.
If you're using iTunes, then you'll be prompted to plug your iPad into your computer. iTunes will then perform essentially the same restore as iCloud, and you'll be prompted to select the right backup to restore. The process is the same, and at the end you'll have a fully restored iPad.