Hello *waves*
I've driven a rental in the US a few times now and the majority of petrol stations will want you to pay first. If you end up at a pump which works the same as our "pay at the pump" ones then it's exactly the same, put card in, put PIN in and take as much fuel as you require. The ones which need your ZIP code, you'll need to go inside and have your card swiped and it's exactly the same, take as much fuel as you need and the card will be charged accordingly. Unless you know that you want to put $40 in (for example), it is much easier paying by card as it does save you that second trip inside.
There are usually a bajillion petrol stations in each town/city anyway, so you'll probably end up at one with pay at the pump, look for the ones which seem newer, cleaner and bigger and you should be onto a winner. It's mainly those in tiny towns with the owner watching you with a shotgun where you might be there a little longer