Making affiliate sales often depends on the relationship you have built with your website visitors. If people trust you they are more likely to buy from you.
Giving website visitors the information they are looking for helps build this trust. This is why building a list of subscribers is one of the best ways to increase your sales of affiliate products.

If you visit any of the top internet marketers websites or online stores, you will more than likely find mutiple optin boxes. These opt-in boxes capture online vistors details such as name and email address. If the marketer or online store obtains these details, they can contact the visitor whenever they wish, so long as the subscriber wants to remain on the list. If they are recieving quality information, there is a good chance they will not want to unsubscribe, and this increases the likelyhood of making a sale to this person now or in the future.

Having a subscriber list means the website owner can contact visitors more than once. If someone visits a website, and leaves again, there is little chance of the them returning, and you have only had one opportunity to advertise to them. However, subscribers are reminded of your products multiple times.

One thing to be aware of is that people don't want to be 'sold to' all of the time. Everyone with an email account knows how annoying spam can be, so you have to be able to provide useful information your subscribers will be intersted in.

It helps to include news, interesting articles, free reports and tips. If it's appropriate, you can add affiliate links or recommend products that way. Also, if you recommend a product it has to be good and you should have used it yourself or fully understand how it will benefit your subscribers.