That’s right, you’re going to want to back up your old iPhone after you have your new iPhone 14 in hand, so the backup is as up-to-date as it can possibly be. You can back up via iCloud, in iTunes (on a Windows PC or older Mac), or in the Finder (on macOS Catalina or later).
For an iCloud backup: No need to connect your old iPhone to your Mac. Just launch Settings and tap on your Apple ID profile listing at the top, then go to iCloud > iCloud Backup and select Back up now.
For a Mac backup (macOS Catalina or later): Connect your old iPhone to your Mac, open a new Finder window, and select your iPhone in the left column in the Locations section. In the Backups section, choose, Back up all of the data on your iPhone to this Mac. Checking Encrypt local backup is a good idea, so your account passwords and health data get backed up too—just choose a password you won’t forget. Click the button to Back up now.
If you need to restore your iPhone or want to restore this backup to your new iPhone 14, just connect it as above and tell your Mac you want to restore from the backup you just made. Later, you can switch back to iCloud backups if you prefer, in Settings > iCloud > Backup. But it never hurts to run a backup on your own Mac every now and then.
For a Mac backup (macOS Mojave or older): The backup process is similar to that described above for Catalina, but instead, you use the iTunes app. After you back up your old iPhone, connect your new one if you want to restore it from there. iTunes will take you through the steps for setup.
When setting up your new iPhone 14, you can restore your iPhone from this backup once you’ve logged into your new device with your Apple ID.
If you happen to be coming from an Android phone (hey, welcome to the garden!), there’s an Android Move to iOS app that can assist you with getting all of your Google account data in Mail, Calendars, and Contacts, moving your camera roll over, even transferring your Chrome bookmarks to Safari.