Please do not take some of these tools serious. I like the one Ridge posted simply because it will go through things step by step with you in regards to things you are missing (check right hand side of page for this feature)
my best suggestion is to read and double check stuff than look at it again and see where you can improve. A page to start although it is dated is
http://www.seomoz.org/article/search-ranking-factors
Linear Mode
