If you're serious about making money online, start a blog. Blogging is one of the easiest and most sustainable income sources. As long as the blog is setup the right way, in the right niche, with the right content targeted at the right audience, and the offer is complementary to the content, you could make a tremendous amount of passive income from a blog.
The products and services you will be promoting to your audience must be relevant and good quality. Make sure you believe in them and know everything about them, because this will be crucial to you delivering the sales pitch to your audience. You need to build trust with your audience so make sure the products and services you choose to promote are trustworthy enough.
Let no one tell you that email marketing is dead. An email list is crucial for every affiliate marketer. You can start building up your email list with a lead magnet (like the information products mentioned previously) or even just by encouraging your audience to sign up for your updates. You can then push your content to this audience via email and also direct them to your affiliate offers. Don't be sleazy about the sales, but if you build up enough trust with your email audience; when the time comes, they will not mind purchasing a product from you.
Affiliate marketing overlaps with other Internet marketing methods to some degree, because affiliates often use regular advertising methods. Those methods include organic search engine optimization (SEO), paid search engine marketing (PPC – Pay Per Click), e-mail marketing, content marketing, and (in some sense) display advertising. On the other hand, affiliates sometimes use less orthodox techniques, such as publishing reviews of products or services offered by a partner.