Attract qualified associates and they will attract qualified customers. Perhaps the most important mistake people make in founding an associate program is not being willing to provide a commission for affiliates. It's true that you won't earn as much discounting sales to your associates. Trust me you will earn it back shortly. Don't require that your associates buy your products, just make it as easy and inexpensive as possible.
Some programs even offer higher commissions on sales to affiliates who own the product.
You need to be able to convert visitors into sales in order to keep your sales associates happy. The ideal associate is someone who already owns the product. A customer will know the product better, they will know how to use it and can provide real-world benefits and testimonials to prospective customers. Some associate programs require that their associates buy the product at regular prices before allowing them to earn commissions selling it to others. Others require that their associates pass a product knowledge test or own their own domain or some other requirement.