If you have an online business and you haven't concentrated on building a mailing list then you really need to start now...today! I'm sure you have mailing list heard the saying, "the money is in the list". Well, it's true, it is in the list. If you sell information products, whether they be your own or an affiliate product then you are going to make money from that one sale.
But what happens to that person once they have bought the product. They just vanish into cyber oblivion and you may never see them again. You then mailing list have to go and find a new customer and go through the whole process again. Just imagine if you had captured the details of the person who had bought the product from you.
Or even if you just got the details of anyone who was interested in your product, you could offer them a free preview of part of your product in exchange for their details. What this now allows you to do is to build a relationship and form a level of trust mailing list with this person by offering them continued value by email. Once they start to form that level of trust with you then they are much more likely to buy from you again.