How to back up your phone before switching to a new one

Your phone backs itself up automatically to iCloud (iPhone) or Google (Android). You just need to make sure it's turned on before you switch. Go to Settings → [Your Name] → iCloud (iPhone) or Settings → Google → Manage your Google Account (Android) and check that backup is enabled. When you set up the new phone, sign in with the same account and everything comes back.

Your phone automatically backs up your most important stuff. Photos, contacts, messages, and app data. To the cloud. All you need to do is make sure backup is turned on before you switch phones. On your new phone, you'll sign in with the same account and the backup will restore everything. It's like having a photocopy of your phone stored in a safe place, and then you just tell the new phone to get it.