There have many ways you can promote your affiliate link.
1)The first and best one is creating a blog or website.
2)You can do article marketing in different directory like Squidoo, hubpages and ezine.
3)Video marketing is another way of promote.Make video on product review and upload them in different video sharing site with your affiliate link.
4)Micro blogging is a good way of promoting your link. Create micro blogs in free blogging platform. Write short product review and place your affiliate link.You can also link back to your site or blog.
5)Social media is a strong and bursting way of promotion.Promote on Twitter, Facebook,Google+ and etc.
6)You can also promote in different forum.It,s effective cause every forum have a large community.