The first stage of a funnel is the "top of the funnel" (TOFU), where you offer something free to entice people to give you their contact information. For example, create a do-it-yourself solution (DIY solution) that individuals may use on their own, then propose a frontend product that offers a paid answer to the same problem. The second stage is the "middle of the funnel" (MOFU), where you offer more valuable content, such as an ebook or report, in exchange for people's contact information. The third stage is the "bottom of the funnel" (BOFU), where you offer your paid products or services.   Finally, the fourth stage is the "post-purchase" stage, where you follow up with customers after they've made a purchase to ensure they're satisfied and to upsell them on additional products.