Following yesterday's hint about fixing an iOS device that wouldn't launch third-party apps, I realized that it would be useful to back up my iPhone via iCloud, in case I have a problem away from home. I looked around, and saw that we don't have anything about this on the site, so I thought I'd write a brief primer.
You can turn on iCloud backups in iTunes: connect your iOS device, then, on the Summary tab, in the Backups section, click on Back Up to iCloud. However, when you sync your device, it won't back up to iCloud. The only away for this to happen is, according to Apple, when a device is connected to the Internet via Wi-Fi, connected to a power source, and has its screen locked. And, this only happens once a day.
However, you can force a first iCloud backup on the device by going to Settings > iCloud > Storage & Backup, then tapping on Back Up Now. (You can also turn on or off iCloud backups here; this has the same effect as the iTunes setting.)
It's worth noting exactly what gets backed up to iCloud. Apple has a technical document explaining this in detail. Note that iCloud backups don't back up content synced via iTunes: music, movies and TV shows not purchased from the iTunes store; podcasts; audiobooks; and photos synced from your Mac. However, any purchased content is backed up (technically, it's just a list of the content), and this content isn't counted against your iCloud storage quota. What will take up the most space in your iCloud backup is photos and videos on your device, so if you're tight on space, think of downloading these to your computer, or uploading them to some other storage service.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20121002015050599