10. Turn it off
This one's a last resort, but if you need an iPhone to survive a weekend or a power outage, and its reason for being powered up is essential communications only, turn the device off when you're not using it. First, that'll stop you being tempted in just having another quick go on Candy Crush; secondly, it'll also ensure even background tasks aren't slowly supping power. To turn your iOS device off, hold the sleep button for a few seconds and then drag across 'slide to power off'.
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