See it from your child's POV. "School" is an abstract concept to a kid who's never been before. So when you talk about the big day, don't make general statements; instead, get into the details. Tell her about the games she'll play, the kids she'll meet, and how you'll always be there to pick her up at the end of the day.
Make a visit. Most schools have some kind of tour or open house. Don't miss this event! While you're there, take pictures (include some of your child with his teacher). Looking at these photos is a great way to get your kid talking about what he's looking forward to and what he's anxious about -- and to help clarify any misconceptions he has.
Talk the talk. School has a language all its own. So rename your everyday activities using preschoolese. When you paint or color, call it "art time" and do it in a designated "art corner." When your child eats her afternoon milk and cookies, it's "snacktime." No more nap -- it's "rest time" (you might even put a mat on the floor).
Invent a voyage. Get him excited about the adventure of the daily trip to school. Will he get to ride on a big yellow school bus? Will he get to spend time in the car with Daddy each morning? Maybe there's a fun walk with Grandma in his future? Narrate the story of how he'll get to his destination with lots of colorful details. If he's not taking the school bus, do a dry run so he'll know what to expect.
Go on a mini shopping spree. Buying her a new backpack, pencil case, and set of crayons will make her feel like a big kid -- especially if she gets to pick out the gear herself. But don't ask your child to save her supplies for school. Let her carry her stuff around and play with her gear right away. You want to make as many deposits in the school-is-fun bank as possible.
Crank up the kudos. Now's a good time to start applauding your kid's school-tastic skills. If you see him share a toy with his sister, say, "I noticed that you gave Jane a turn with the ball. That made her very happy. Your new friends at school are going to really like it when you share toys with them." And don't worry about raising a praise junkie. You'll just be making him aware of some of the things that he's already good at so he feels less overwhelmed.
Meet the parents (and the kids). It's intimidating to walk into a room full of people you've never met -- and then have your mom and dad leave! If you can, get a class list, or if you know parents of other children who'll be in your child's class, arrange some playdates so your child will be able to adjust to the social scene.