Why bother buying a brand-new pack of pencils when you have oodles of No. 2s sitting in your kitchen drawer?

"Chances are, you probably have binders, colored pencils and highlighters left over from last year," says Joanie Demer, a savings expert and co-founder of the blog The Krazy Coupon Lady. A few pens here, a sheaf of paper there -- these small already-have-its can add up to big savings on your school supply list.

Likewise, making an inventory of your student's wardrobe can also prevent overbuying. Often, parents will go on a back-to-school clothing shopping spree at department stores, forgetting about the perfectly good sweaters and pants lying forsaken in the backs of closets, says Stephanie Nelson, founder of the website CouponMom.com. Nelson suggests identifying the school clothes that will still fit your child -- that they will still agree to wear -- and donating the rest to charity. "Once you look at the clothes you have, the list of clothes you're going to need is going to be cut in half," Nelson says.