1. While you ship customer the first product they bought, insert a flyer or leaflet for your back-end product in the bundle.
2. Offer customers a free subscription to a customers only e-zine when they buy your product. You could include your ad for your back-end product in each issue.
3. Mail your customers greeting cards on their birthday or special day. Include a small advertisement inside the card for your back-end product.
4. After customer order your first product from your web site, provide them to a "thank you" web page and include your back-end product ad on that page.
