1. Visit the school's playground as much as possible and peek in the windows.
2. Make time during the week to go inside the school. I dropped off updated immunization records and got a little tour down what my daughter called "My hallway."
3. Engage in "school" crafts. Lots of ideas online.
4. Pack that bookbag! I don't have a supply list nor do I know who her teacher will be but we bought a bunch of supplies she may or may not need and I let her pack them up.
5. Read "my first time in school" books.
MOST IMPORTANTLY, TALK TO HIM AT EVERY OPPORTUNITY ABOUT SOMETHING SCHOOL RELATED BUT BE CASUAL AND BRIEF. WHAT MIGHT HIS TEACHER BE LIKE? HOW MANY KIDS IN THE CLASS? HOW IT'S GOING TO BE EVERYONE'S FIRST TIME THERE. WHAT HE MIGHT DO THERE; PAINT, PLAY IN THE PLAYGROUND, MAKE LOTS OF CRAFTS, ETC.
BTW, it's my daughter's 1st time too and she's VERY excited. I hope when the day comes she'll be okay with me leaving. I anticipate being enough of a mess for the both of us :-(
Good luck! Hope this proves to be helpful.
Oh, one last tip, my sis-law suggested not using words like I'm going to leave you there and pick you up later. She said it would be better to say something like, "You know how mommy goes to work everyday - this is going to be the same thing, etc."