Some regional-based search engines or indexes will only list sites that are registered
in their country code. If your site exclusively or primarily caters to a specific
country, then you will most likely want to register a domain using the local country
code.
Some search engines will still show your site in regional based search results if your
site is hosted within that country, has links to and from other local sites, and/or has
your address and phone number in the page text, but many directories are
extremely picky and will only list regional domains.
As search progresses, localization of results will become more common. Some of
the major search engines already give sites a regional ranking boost based upon
where the site is hosted and the domain extension.
If you develop a regional domain (.co.uk for example), I also suggest buying the
.com version of your domain, if it is available, and forwarding it to the regional
domain you registered. By buying the .com version and forwarding it your site, you
help retain traffic you may have lost by people forgetting to put your region
specific domain extension in their address bar when they type the website address
directly into the address bar.
I prefer to use a .com version of a URL over other generic TLDs. People may
assume your site is a .com even if it is .net, .biz, .org, or .info when they go to look
for it on the web. If all they remember is your domain name, they may type your
domain name followed by ‘.com’ because ‘.com’ is the default TLD in most
people’s heads. If you don’t own the .com version as well, you are giving some of
your hard-earned traffic to a competitor.
If you are running a charity or organizational website a .org may be seen by some
people as a sign of credibility.
It is a good idea to place your business location on your web pages. If you are in a
country where the search technology is primitive, local searchers will frequently add
the country or city name to their searches, and if you have them on your pages you
stand to be returned as a relevant result for more searches.