2 Clean Up Your Device
Right before an iOS update is a good time to do a bit of spring cleaning on your device. Chances are that there are quite a few apps, photos and other random bits of data that you don’t really need anymore, so go through and delete the unnecessary ones.
This is an especially critical step if your device doesn’t have much remaining storage — and you’ll need some to even download and install iOS 11.3. While iOS 11.3 isn’t as big of an update if you’re running iOS 11 already, it will be fairly large if you’re upgrading from an older version of iOS.