Improving SEO

Improving Search Engine Optimisation can result in more quality traffic from search engines, and more business for your site. SEO is now a massive industry in itself.

Basics

If a website cannot be seen by search engines, all other SEO is moot. Therefore, as the top priority, you must:

Check your robots.txt file allows search engines to visit the relevant content pages in your site.
Ensure site content is spiderable via links alone.
(Optional) Provide a Sitemaps file listing pages from your site.

Consider the following in order:

Do I need this keyword? Some keywords will be staggeringly difficult, if not impossible to score highly for. If the companies ranking at the top work hard to stay there and have 10 x your budget, you may be wasting your time. Resources may be better allocated towards easier battles which could pay off better.
What are others doing to score highly for this keyword? The key things to look for are: size and quality of content, relating to the keyword. Some websites may have blogs, reams of articles, newsletters and forums on nothing but your chosen keyword. You'll probably need to match or exceed that commitment to outrank them.
Build the best website for that keyword. Essentially, all search engines are trying to give users the best possible pages for a specific keyword. If you enter "used cars" into Google, their interests are best served by you seeing the best possible results for used cars. Putting aside all of the (short lived) tricks of the trade, the best way to score highly for a term is to have the best website relating to it. Such websites rarely have to battle hard to score more highly – they need only to keep their standards up.

In Sitescore, your overall optimisation for search engines is rated by the Search Score summary.