You can use your marketing skills to show business owners the benefits of using analytics data, strategic keywords and content structure to gain more organic web traffic. If you are unfamiliar with SEO or want to brush up on your digital marketing skills, you can reference Moz's Beginner's Guide to SEO. Keep in mind that Google's algorithms are always changing, so SEO is something you will need to continue your education on to stay relevant and successful in this field.
The internet changes so fast that one year online equals about five years in the real world. But the principles of how to start and grow a successful online business haven't changed at all. If you're just starting a small business online, stick to this sequence. If you've been online awhile, do a quick review and see if there's a step you're neglecting, or never got around to doing in the first place. You can't go wrong with the basics.