Our local store does a lot for the local middle and high school XC teams. The first thing you see when you go in is singlets from all of the local middle schools, high schools, and small colleges in the area. They come out and give a talk about types of shoes and spikes, and they'll do basic gait assessments at practices. They give 15% discounts for kids on local teams. Our boosters program also buys a bunch of gift cards for the end of the season banquet, but the store usually donates two or three as well.
Obviously some of these things will cost you a money, but they get kids into your store and make them regulars.