Visit the school over the summer. Play at the playground, ride bikes on the premises-- or at least walk by if it's locked up for the summer. The more familiar the school becomes, the more the child's anxiety is relieved. Point out the kindergarten building or floor, if there is one. Take this opportunity to identify where you'll be picking up the child at the end of the day, too.
Ask the child what's making her feel afraid. Children of this age can be surprisingly articulate. Many preschoolers, especially those with older siblings, may be feeling stressed about academic expectations, including homework and the ability to write the alphabet. But kindergartens are set up to teach those skills; they're not required upon entry in most states. Be clear with your child about what's expected of her, and make sure she knows that kindergarten is a place to learn.
Talk about what you know. If you know the school, the teacher or other kids in the class, talk about them. Explain how the drop-off process works, if you're already familiar with it. Surround your child with as much information about his first day as you possibly can. The more he knows, the better he will feel. If you don't have firsthand knowledge, meet for coffee with a family that's been there before and ask them how the first day of school goes, what the teacher is like and what supplies, if any, your child might need on the first day.
Set up playdates with other kindergarteners in the neighborhood. Though not all of them will be in your child's class, a familiar face on the playground the first day or two will make her feel much more comfortable about starting kindergarten.
Keep your emotions in check. While you may be cartwheeling for joy at the prospect of having your child start kindergarten, you may also be feeling quite sad. Don't let your child know too much about how you're feeling; give him the space to begin experiencing this process himself. As much he looks to you for guidance, he'll read any tears as a sign that something isn't right, which will increase his anxiety tenfold.
Ask for your child's input. If you know she is feeling anxious, get her to tell you what she'd like for snack, what she'll wear that first day and what shoes she'd prefer. Give her control over some aspects of the beginning of kindergarten, and you'll find that her anxiety will diminish.