Advertising is one part message, one part delivery vehicle. Signs, T-shirts, newspapers and billboards are merely delivery vehicles. The key to success, however, is your message. My suggestion is that you open with a provocative question in large letters, such as, "Could Your Kid Become an Actor?" This would be followed by the name of your organization and your phone number or the name of your website. The fact that your organization is non-profit is irrelevant. Your delivery vehicle will be determined by your budget. Put up a billboard if you can. Smaller signs and T-shirts are an option if the budget does not allow for a billboard. Good luck to you.