If you have a web site, make sure that you are registered with Webmaster Tools. It is free and is a Google product.
In a nutshell, Webmaster Tools is a site that can run diagnostics on your web site to make sure that it contains all the elements needed for the Google search engines to find, and index, the pages on your site.
Most importantly, if your site is functioning properly, your web page will attain a rank. This rank is very important in determining the visibility of your site on a search.
Submitting your site on Webmaster Tools is not essential, but it is helpful and I'd recommend it to both established webmasters and new.
If you already have an established site, submit it to Webmaster Tools. It will analyze all of your internal links, but more importantly alert you to "dead" links. Links are an important way that your web pages become connected. Links tell the search engines about new pages.
Submitting your site will also ensure that your web site has been found. It is possible that the Google engines don't know you exist.
Not all web site are indexed or suitable for Google. If your site has some fatal flaws, Webmaster Tools can tell you.
The other point for experienced webmasters is to make sure that you submit a sitemap (a file containing a list of the pages in your site) to Google. This is easily done within Webmaster Tools.
Sitemaps are basically a listing of the pages in your site. If not all the pages can be indexed by the search engines, you'll want to find out why.
Webmaster Tools is essential for the beginner. Even if you have yet to start, reading the help articles within Webmaster Tools will give you an idea of what Google expects to find in a properly configured site.
You might as well start fresh knowing what the rules and guidelines are to constructing a site that can easily be found and indexed by the Google robots.
If your site cant' be found, indexed and ranked by Google, your site will basically not exist. Webmaster Tools is a great resource for tuning up or creating a new site.