3 primary components to a successful website
1. Conversion rate, maximizing the number of people who visit your site into actual leads. It would take a book to write about this subject alone but in a nutshell, it should be easy to read, be full of "call to action's", and tell a customer why to choose you.
2. On-site optimization. Each page of your website should focus on one or two keywords max. Don't stuff your home page full of 10-15 keywords, it will dilute it. Figure out what your best keyword is for your area and focus your home page on that. Sub pages can then be used to focus on other keywords related to each service your provide. Your browser title is very important, this is the heading that shows up in Google search results. These are tough to write because not only do you want it to catch the customers eye but you also want it to contain your keywords, and preferably stated twice in a short phrase
Each page that your are focusing on a specific keyword should contain that word (or variations of it) at least 3-4% of the total words on the page. You should have H1,H2, and H3 titles in your page. Also your meta description for each page should be well written...this is what shows up below the browser title in your google search results.
Try to make the first few words and last few words that the google bots see on each page contain your keywords
Don't overload your site with pictures and DON't make the pictures to big and slow down how fast the page will load...Google doesn't like slow loading sites. Also make sure every photo has an Alt description for it...this is the little text box you see when you hold the mouse over a picture.
There is definetely and art to writing a easy to read site for a customer AND making it optimize well for Google....
3. Off page optimization - This is the most important component to driving your site to the top of Google results. Facebook, twitter, RSS feeds, Blogs, articles, citations, youtube videos are all important tools to create backlinks back into your site. Your looking for do follow links into your site. Don't get involved in link trading.
Lots more about all of this but I hope this helps a little....