A classic to understand SEO :: A bit more technical, but still helpful and clear, explanation of Search Engine Optimisation for serious beginners by MOZ.com

    SimDif essential guide :: A more detailed (but I hope still simple) version of the method explained here.

    The Usability Bible :: When it comes to understanding users in front of machines, the NN group is the supreme reference.

Tools

    Google trends :: For when you can't decide between 2 expressions and would like to know which one is most likely to be used in a Google search.

    24 simple & useful tools in SEO :: A great and relevant collection of tools. Don't take everything literally, but try them all.

    More technical Options :: Some of us see SEO as a sport, and some of the options here are for serious amateurs ;-).
Some of us would also say that you'd better spend more time building a relationship with your clients than "optimizing" your website.

Definitions

    Googlable :: When was this term first used ?

    Googlable :: in the Collins Dictionary

    Googlable :: In the Urban Dictionary

Backlinks

    What is a backlink :: Moz.com again, a clear simple definition of a back link.

    become serious about back links :: Quality backlinks often start with colleagues, local directories, professional associations, ...
Now you too can think about them in a deeper way.