First Time Out: Checklist
Good for you! Yeah, it's time to get out on the water!
Couple questions: does your buddy know how to sail? Are you on a lake, bay, or ocean?
You'll definitely want a detailed chart of the area. You'll also want a VHF radio and a cell phone if you get into trouble. Make sure you learn how to use the anchor and make sure it can be deployed quickly.
Check your weather forecast. Make sure your first day isn't too challenging with either calm winds or winds much over 15 knots. Take a bag with water, snacks, and sunscreen. If your weather can change fast, make sure you have a change of clothes for any condition. You might want sailing gloves, too. I'm sure you'll get a ton more suggestions, the above are a few to get ya going. Have a blast!