Bring a clear fault description
Note when the problem began, whether the device was dropped or exposed to liquid, and any previous repairs. Mention if the fault only happens with one charger, accessory or app.
Make a backup when possible
Check that your backup is current before leaving the device. If it will not turn on, tell us whether recovering data is your priority before authorising other work.
Keep control of your accounts
Do not send Apple account passwords, one-time codes or banking information through a contact form. Enter credentials yourself when a legitimate testing step needs them.
Confirm the work
Ask about the diagnosis, part choice, price, expected time and repair-specific warranty. Discuss any erase or reset separately.