If you have built up an email list, you could also promote your affiliate offers via email promotions. Just make sure you build up a relationship with your audience first instead of going for the hard sell straightaway. The emails you send out must contain your affiliate links to products so when your audience click through. the sale is attributed to you.
If you are a confident web developer then designing your own themes is an obvious path to follow if you are looking to make money online. ThemeForest sells a wide assortment of developers themes, including themes for WordPress, Shopify, Weebly, and Tumblr, to name a few. Once you have created your theme, get it accepted onto the ThemeForest marketplace and make money each time it sells.
The problem with affiliate marketing, like many other home business options, are the so-called gurus and get-rich-quick programs that suggest affiliate marketing can be done fast and with little effort. Odds are you've read claims of affiliate marketing programs that say you can make hundreds of thousands of dollars a month doing almost nothing ("Three clicks to rich!"). Or, they suggest you can set up your affiliate site, and then forget it, except to check your bank deposits.