Dress well - even if it's a hoodie and sandal type office, wear a button down and jeans the first day
Pay attention to tax forms, direct deposit, etc... - if you have questions, ask
Try to be social - shake hands, try to remember names - the old repeat their name after they say it trick helps - ie: "Nice to meet you, Joe / Jane".
Bring a lunch if one isn't previously planned
I wouldn't bring family pictures or fidget spinners or fancy coffee mugs or potted plants on the first day. See how others have desks / cubes / offices decorated and do that stuff on day 2 or 3
Go easy on the coffee if you drink coffee. Some drink a pot a day; maybe have just 1 or 2 if it's provided, lol... Or - bring your own if you need it (again, get the lay of the land first day). Conversely, go easy on the water. You don't want to be running to the bathroom every hour, haha.
Be attentive - listen when people talk to you; if theres training, try to stay focused and sharp
Your first day, your learning. Don't put down how people do stuff, don't suggest redoing X or they should use X instead of Y.