For search engine optimisation to truly work it is best not to cherry pick from the tree as it could result in a great deal of time and effort for little result when smaller changes from an SEO professional will have a much larger impact.
The most common tips given for search engine optimisation, for example, are to grow content and get links. These are factors however many of the websites that dominate the rankings fail in these areas.
Yes content is good in that it provides more chances that one of your pages will be found but it can also dilute core keywords.
So if you have a website about coffee makers that features brands A, B and C, and you add brand D this is positive content. But if you add tea maker brand A you dilute the keyword "coffee maker" and stand a good chance of being ignored for both.
So if you already have a website that you are convinced as useful and unique content then before expanding it further or chasing links you should ensure that it is as search engine friendly as possible. This may be all that is required.
The steps do do this can be found on the page Plan your SEO process
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.