Your website should have a theme and be focused on content. Make sure the affiliates you choose fit well with your theme. For example, perhaps your website is about Classic Silent Films. On the website you could have a list of recommended reading. Remember to keep you website current with frequent updates - you will need to give visitors are reason to keep returning.
M ake sure the price is right.
It is critical to know what the terms will be. Target you marketing to your audience. Too many websites have banners for every product ever offered for sale. Too often the products offered have no relation to the content of the website. The banners should be targeted to the audience that is visiting your site.