And always make sure your websites or blogs always have an opt-in form on them offering your visitors something of value, like if you are selling web-hosting, offer them a course/ebook via email subscription on how to set up their own blog step by step, inside the course/ebook you give them your recommendation for a webhost provider and where to get a good theme.
This way your offer ties into what you are selling, and provides the how to, that people need. And now that they are on your email list you can suggest other products and services that you are selling that compliment your offer, and what they further need to grow their business.
If you build your email list with your traffic and do this right you will build life long customers who purchase from you many times.