Google's Search Engine Optimisation (SEO) Start Guide is a great introduction to optimising your website to rank well in their search engine.
It includes best practice advice such as:
- the importance of unique, accurate page titles
- using the "description" metadata tag
- how your URLs and navigation effect search
- how to optimise your website content (text, links and images)
- understanding how Google reads your site
- SEO for mobile phones
- how to promote and analysis your website.