Gather Your Important Info
Putting in a Galaxy S9 pre-order will require more than just your credit card number. You will need some very specific information on hand and it's important to track down this info before the pre-order date.
At the very least you'll need to have your carrier login information ready. That includes the user name and password. If you aren't the primary account holder, make sure you get that information ahead of time.
Make sure you have your Social Security Number (or the account holder's SSN), and the account billing information ready to go when you go to order.
Some carriers might require you to ship your pre-order to the primary billing address so if that's not your current shipping address, you'll want to address that before the pre-order date.
If you plan on going into a store, you'll need this information as well. You also might need the primary account holder to authorize you to make the purchase so make sure they look into that ahead of time.