Do Plan in Advance

There are a few things you can do before ever doing a search for a domain name:

• Consider whether you want a domain name that's never been registered or if you don't mind (or would even prefer) an aftermarket domain name. If you need to get going quickly and need a domain name with established traffic, an aftermarket domain name might be for you.

• Do decide which top-level domain (TLD) or domains you're comfortable using. This choice includes general TLDs, like .com, .net, .biz, .org, .info and country codes like .us, .uk. Be aware that either you or your business may have to be in a country in order to register a domain name with a country code. Although you will see TLDs like .gov, .edu, and .mil, the use of these is restricted to the US government, educational institutions, and the US military respectively. If none of these seem to work for you or you need a domain name more specific for your type of business, explore the other possibilities like .coop, .jobs, .mobi, .pro, .tel, and .travel.

• Do brainstorm some possibilities. Especially if you want to be the first person to register the domain  name, spend some time coming up with workable websites. If you have a brand name or a registered trade name, you will probably want to use it in or as the domain name. If you have multiple ideas in advance, you will likely experience less frustration than if you go in with one idea and it's already been registered.

• Be aware that if a domain name is registered, it may be available through the domain name aftermarket.

Don't Use Another Company's Tradename

It's illegal, so don't do it. Your soda maybe be the best in the world, but your website cannot be named http://betterthanPepsi.com

Do Choose a Few Memorable, Short Words

• You can only use the letters of the alphabet, the hyphen or dash, the underscore, and the digits 0-9. Note that Matt Cutts of Google recommends using dashes rather than underscores because of the way searches are processed: basically, you'll show up in more search results if you use dashes rather than underscores.

• Think about what your core customers will be looking for when searching for your domain name.

• In most cases, leave out words like and and the.

Do Use a Legitimate Domain Name Registrar

Domain name registrars for general TLDs are accredited by ICANN, the International Corporation for Assigned Names and Numbers. Those for country TLDs are licensed by the country. Use this list to find

Sources

http://www.mattcutts.com/blog/dashes-vs-underscores/