Send one copy of the invoice to the coach or sponsor, one to the bookstore and one to the district. Be aware of their payment date and do not be late in mailing the invoice. Always follow up the billing with a phone call to make sure the sponsor has turned in all the paperwork and the bookstore has sent the paperwork to the district and that district has received it, etc. Consider holding any incentives or prizes until after you have been paid - as a motivator. Two other areas to mention quickly are doing direct mail to schools and attending and exhibiting at teachers and coaches conventions.
Direct mail can be an easy source of lead generation.
You can mail to dozens of campus clubs and offer a business reply card or toll free number for response. Coaches, teachers, activity directors, band instructors and others all attend workshops and conventions where vendors who sell them products exhibit their items. These are very similar to our industry trade shows only on a much smaller scale. By exhibiting at these with a very professional looking display you will generate hundreds of leads from schools through-out your region. To find out more about specific events contact you schools activity director.