The best place to start when doing seo is to start with your “on page seo”. On page seo is making sure that your site and all of its pages are optimized for Google. Things like page titles, meta Info, headings, on-page keywords, url structure, and linking structures are all ways you can help better your chances of ranking better with google. In order to take advantage of other advanced seo techniques you must first start with your on page seo.
There are many tools that will help you determine issues with your sites on page seo.
My favorite is seomoz it can crawl your site and let you know of any on page issues, it also tracks your progress in rankings over time for keywords you control. There is a free 30 day trial which is a great way to check out all of the seomoz seo tools. Also you can view on page site errors.