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Block persistent callers from contacting you
Calls significantly drain your battery meter, even if you don't pick up incoming calls. If you get the same persistent person calling, you can now block them from reaching you.
To do this, head back to Settings and scroll down to Phone. Scroll down further to Blocked and select the contacts you wish to automatically refuse access. While this feature blocks the call coming through, it doesn't prevent the caller from leaving you a voicemail.
Prevent your iPhone from 'learning' your frequent locations
Your iOS 7-powered iPhone from the get-go records where you go so it can pick out nuggets of information that may help you, particularly if you visit those places regularly. It updates the Today section in your notification center, and can give you estimated times of arrival to your destinations. While it's a handy feature, it is far from absolutely necessary, and can be turned off to save some valuable battery.
Buried deep down in the device's settings, you have to navigate to Settings > Privacy > Location Services > System Services, then switch off the Frequent Locations option. You can also delete any data already collected by tapping Clear History at the bottom of the screen.
Turn off 'parallax' motion user interface
If you slowly jiggle your iPhone in your hand, you may notice the "parallax" effect of three-dimensional icons sitting on top of your wallpaper. This effect uses internal hardware to sense the direction, speed, and motion of your movements. This, as you might expect, will drain the battery. Though flashy and visually quite cool, it's not wholly necessary if you're a power user.
To disable the "moving wallpaper" feature, head to Settings > General > Accessibility > Reduce Motion, then flick the switch in the on position.