Lessons learned from my son and his moving experiences (he shared a house or apartment with friends a couple of times, then moved into a very small place when he went to college):
1. Get him a small safe/locked box/small sturdy filing box, and help him realize the importance of storing necessary papers/documents in one place. If he protests that these are his friends and wouldn't steal anything, teach him that this is about staying organized. He'll have one specific place for the stuff he can't lose track of (checkbook, receipts for computer, etc).
2. One thing that really surprised me was the number of my son's friends who didn't know who their car insurance was with or how to contact them, whether they had health insurance, if they had renter's insurance, etc. Have your son create a folder or app on his phone or somewhere safe where he can list the important numbers: roadside assistance, car insurance, doctor, etc, and make sure he knows the procedure in case of a break-in, a car accident (his own or someone else's). So many of my son's friends said things like "yeah my dad has insurance on my car, I guess" and that was the extent of their knowledge. Have your son take the initiative in informing any of these types of companies of his new address, and stress the importance of updating whenever he moves.
3. If he will be driving, prepare a small bag/box to keep in the trunk of the car. It should contain gloves, maybe a fold-up poncho in case of rain, flashlight, batteries, energy bars, a couple of bottles of water, duct tape, a couple of dollars and quarters, and other "stranded in the dark on the side of the road" kind of emergency supplies. My son always thought that was stupid until his car broke down and it was cold and dark.
4. The best trick my son learned at college was about dry-erase whiteboards. He needed one to diagram technical stuff that he was studying, and whiteboards are ridiculously expensive and small. Other students told him to go to Home Depot or Lowes or similar stores and buy a melamine board, in the bath/shower department. It's just a few dollars for a huge board and they'll cut it for you. And it's a perfect dry-erase white board. He used clips to put it on the wall and had an entire whiteboard wall. They make great message boards for roommates, and reminders about the rent being due, etc.
I agree with waiting a while to figure out what's needed and what really isn't, as far as furnishings.