Good question! Where I’m working at, it’s generally three things: the first, wear your mask, of course. Starbucks also provide a couple different types, in case you don’t know.

Second thing you’ll do when you get there is to take your temperature and sign in the forms next to it, which includes the date, your name, a couple of y or n questions (you’ll generally say ‘yes’ if you don’t show any symptoms, so don’t worry about the questions that you only need to answer if you do show symptoms), your signature, and a notes section (I like writing my confirmed temp on here, since it’s useful info, but that’s kind of just me). On your first day, you’ll most likely answer more questions on the iPad, but you’ll only see that again if you’re showing systems.

Than thirdly, keep up with cleanliness as best you can. If you’re working at a really busy store with minimal staffing, it might be pretty difficult to keep these as clean as it could use. Don’t be discourage, though, because if you wash your hands for 20 seconds often enough, you should be ok. Sanitizer is useful, too, especially for when you need to clean your hands quickly after handling cash or cards, but make sure you give your hands a good wash after a rush to ensure all the germs are off, as sanitizer can only do so much.

TL/DR Just be considerate on all form cleanly and you should do just fine.
I hope your first day goes well! And if you need anything more advice, I’ve got a couple of years under my belt, so I should be mostly helping.