Google Webmaster tools is a set of free tools that every website owner should use. It provides data about crawling, indexing and search traffic and allows you to receive notifications about problems on your site.
Perhaps the most important aspect of setting up your Webmaster Tools account and claiming you website(s) is establishing a communication channel with Google. For example, one of my client’s websites was declared by Google as having “unnatural links”. The only for Google to let my client know about it and allow him to make the required corrections is via the webmaster tools messaging system.
Setting it up is pretty simple. If you have not done it yet, visit my post about how to set up your webmaster tools account and follow the instructions.
Following is a list of my favorite usages of this amazing set of tools:
Submit your XML site map
Google Sitemaps is an easy way for you to help improve your coverage in the Google index.
Creating your Sitemaps is easy when you have a WordPress website. There are few plugins that will do it for you. I recommend using either XML Sitemap Generator for WordPress or WordPress SEO. Both plugin enable you to create an XML site map. All you have to do is go into the Site onfiguration/Site map submenu and submit the address of the xml sitemap

Define your target market
If your business serves a specific geographic market, make sure you define that market .
This can be done inside the SiteConfiguration/Settings sebmenue

Monitor your site ranking for all the search terms it is ranking for.
The Your site on the web/Search Queries sub menu allows you to see exactly what page/position your site appears on for all the search terms it is ranking for.

Define preferred domain structure ( with or with out WWW )
I have dedicated a whole post for this topic. Check it out here: Make your decision WWW yes or no
Why I do not use themes’ built-in SEO functionality
The impact of title and description tags on your website traffic
