Here are some things that I have not seen mentioned on this thread yet.
- Facebook - Important not only for updating customers and brand recognition, it is becoming increasingly more important to get you noticed on the search engines. Not only will your Facebook page rank very high in search listings, it will also show one of your page status updates right on google. It will also show the "about" section of your Facebook page on Google. Fill your "about" section on Facebook with keyword rich content. Update your Facebook page often with status updates and links. This will tell Google that it is active and not forgotten about by the owner.
- Twitter - Just as important as Facebook. Helps your search engine ranking and branding. Tweet often for best results.
- Google+ - Possibly one of the most overlooked social networks but becoming very important in regards to seo. Similar to Facebook and Twitter, update often with posts and links. Fill your "about" section with keyword rich content because this section will be shown on google listings. I see this particular social network becoming a bigger part of Google's search engine ranking placement in the future.
- Google Local - Formerly known as Google Places, this GREATLY helps your SEO! I HIGHLY recommend getting a Google Local page up and running. As you will see in the image below, it can take up huge real estate on a Google search. Also, getting customer reviews on your local page will multiply it's effectiveness. Google wants to give relevant, quality results to it's customers. Having many, great reviews pre-qualifies you to a higher organic listing than those who have no reviews or no reviews. General rule of thumb, have 2-3 more good customer reviews on your local page than your local competition. One way to get reviews is to offer customers a coupon for giving you a review. Might sound silly or stupid, but this could help you get many new jobs in the future and is worth the expense of discounts in a form of coupons.
- Yelp, Superpages, & other online review sites - Similar to the benefits of a Google Local page, the reviews help bigtime! With these sites, often your company review ranking and a featured review is featured right on a Google search page. Get those reviews!
- Blog - Have a company blog! Greatly improves your seo! Have your blog link back to your main site in some way. Many blogs like Tumblr. will have your latest blog post in the Google search listing as shown below.
That is a short list that can help your website without having to change your website yourself. This along with an seo optimized website should provide nice results over a few months. Let me know if you have any questions.