Have Your Login Info Ready
If you're moving your phone from iOS 11 or an old version of iOS 12 to iOS 12.4.1 your device might prompt you to input your Apple ID/iCloud account details and your passcode.
Most of you should know these by heart, but if it's been awhile since you had to login or if you're installing iOS 12.4.1 for someone else, you'll want to make sure you have that information readily available.
There's also a chance some of your apps and services will log you out. If you want to complete the iOS 12.4.1 installation process in the shortest amount of time, make sure you have all of those logins ready to go when you hit update.
Having these handy will help you avoid wasting time.