This is a great article on the effective methods of Search Engine Optimization. SEOmoz collected the opinions of the 37 top SEO experts, and compiled them into one document. They broke them into the top 10 positive factors (i.e. the ones with the most impact), the most controversial factors (i.e. the ones the experts disagreed on the most), and the top 5 most negative factors (i.e. the things you should not do more than anything else).
Now, you need to take this article with a grain of salt… these are people talking about how they get paid. Are they telling you the whole truth? Did they pick the most complicated ones to boost the importance of their own services? Some people say that there will be no need for SEO in the future anyway. As long as there are search engines, there will need to be a way to categorize data and retrieve it. I have digressed. The future of SEO is for another day.