One's website is identified by their domain name so taking the time to pick a good one is very important. Domain names should be both relevant to the subject of the website and easy to remember. The shorter they are the better. Search engine optimization also favors short, relevant domain names. These quality domain names are often hard to find due to their importance, which isn't at all surprising.
Everybody wants, say, pizza.com, because it's short, relevant, and easy to remember. The problem is, only one person can have pizza.com and that person already has it so somebody else can't buy it. However, there are plenty of good domain names for somebody who wants to make a website about pizza that have yet to be claimed. Finding them, really, is the hardest part of the battle.
The Google Adwords Keyword Tool
The Google Adwords Keyword Tool makes far easier the task of choosing a good domain name. If one knows what people are searching for, it's easier to find a domain name that's right on topic. Google's tool provides just this information and more, making the task of choosing a good domain name easier.
Let's say one wants to make a website about Avril Lavigne. Simply type "Avril Lavigne" into the tool and click "Get Keyword Ideas" below the captcha. A list of relevant keywords and their search frequency will be provided. Notice that "Avril Lavigne Music" gets quite a bit of searches in the United States every month. A good domain name for somebody who wants to make, say, an Avril Lavigne Music tribute page or lyrics page, would be avrillavignemusic.net, for example. At the time of this writing, that domain name is available.
Choosing a good domain name is simple and easy with the Google Adwords Keyword Tool. For the main page, try to include that term inside of the <title> and <h1> tags of the page as well to further demonstrate relevancy to the search engines. This should help one's site rank higher.