We all know that Google Webmaster tools provide lot of features that helps you to analyse and optimize website in terms of speed, SEO etc. Moreover it also provides ways to find and resolve structural issues.
Geotargeting or setting geographic target in Google webmaster tools helps you if your site targets users in a particular geographic location. This is particularly useful if you maintain a website or blog which targets a particular country or geography. For example if your website provides services that targets a particular country, you can geo-target that country.

How does Geotargeting Helps Your Site?

First of all Geotargeting is an option in GWT and thus it affects only the Google search results. When you provide Google the target geography for your website, that information will help Google determine how your site appears in search results.
According to Google webmaster tools,

“This data supplements our existing information, and setting a geographic target won’t impact your appearance in search results unless a user limits the scope of the search to a certain country.”

Usually Google determine the geography details based on the websites domain extension. For example if you have a site with country domain (.ca,.co.uk,.in) Google uses this information to adjust its search results. Google also uses information such as IP address, relevant information from Google Places etc to determine the geography priority.

Can You Set Geographic Target for All the Domains?

The answer is no. If you have a website with country level top level domain, you cannot associate target geography. This is because you are already associated with a geographic region.
You can geo-target sites that have generic top level domains. For example, www.globinch.com can set the geography target as United States to influence the appearance of Globinch content on Google search results.

Is It Worth Setting Geographic Target for Your Site? How Do You Setup Geotargeting?

It Depends. If your website is targeting audience of a particular country, then the site is a right candidate to set geography targeting. But if you are maintaining a technology blog like Globinch, it may not be a good idea to target a particular geography. So the deciding factor is the target audience. A website which gives localized information is the best candidate for geotargeting.
You should have the Google Webmaster account to set the Geographic Target for your site. You can see the option under “Site Configuration” menu link. See below.geotarget-website
It is always a better idea to geotarget sites that is provides highly localized information. But for others geotargeting may produce negative results. But you can always reset your target geography preference in Google Webmaster Tools account. So you can try if you really want to experiment it and can reverse it if the final result is not positive.