iOS 12 doesn’t have a super long list of new features, with Apple focusing on improving the overall performance of iOS devices instead. There are, however, some improvements to Siri, a new Screen Time feature, and more robust notification controls.
Updating your iOS device takes just a few minutes, but before you begin mashing the update button, take some time to get your phone or tablet ready.
Get rid of unused apps
I think we can all relate to downloading an app or game just to check it out, and never opening it again. Before updating, go through the apps on your device and remove any app you no longer use. Each app is only taking up storage space and cluttering up your home screens.
Back up your photo library
Should something go wrong during the update process and you wind up restoring your device, you don’t want to lose any of your photos or videos in the process.
The best way to avoid this happening is to use a photo backup service like Apple’s iCloud Photo Library or Google Photos.
Apple’s service is built into iOS, but depending on how big your library is, it can cost you money each month for storage. Google Photos is free, as long as you don’t mind that it doesn’t back up the full-resolution versions of your photos or videos.
Clean out your storage
Open the Settings app then select General > iPhone Storage (this option will reflect the type of device you are using). Let this setting’s page populate, and then try to clear up any excess storage being used by an app.
For example, if you convinced yourself you were finally going to start listening to Podcasts and downloaded a bunch of episodes, but eventually stopped listening — you might want to clear those out.
Back up your device
Finally, with storage cleared, apps deleted, and precious memories stored safely off of your device, it’s time to back up your iOS device.
The easiest way to do this is to go into Settings and select your name at the very top of the Settings app. Next, go to iCloud > iCloud Backup > Back up now. Make sure you’re connected to a Wi-Fi network and it’s a good idea to have your device connected to a charger as well.
Alternatively, you can use iTunes to back up your iOS device with an encrypted backup. This process eliminates the need to enter account passwords if you have to restore or set up a new device down the road. Follow the instructions.
With all of that done, you’re ready for iOS 12. Follow.
Source : https://www.cnet.com/how-to/how-to-prepare-your-iphone-for-ios-12/