The Best / Right Extension.
Extensions are the .com, .in, .net, .org, .info, etc. All of these extensions can be easily searched by our domain name availability. But it is always the .com which is most popular and widely used. If you get a domain name with .com extension, you can increase its chances of popularity. This extension looks more legitimate and common.
The Key or Keyword.
Choice of domain name should involve right keywords. These keywords can only make your website search engine friendly. Be careful while choosing right keyword for your domain name, it should have relevance and searched by your target audience. Consider to choose short domain names, this gives your visitor ease of recalling your domain name.
The meaning of Relevant
Be relevant in your approach. Whatever name you want to register make sure it has some relevance with your business. Search engines will recognize your worth only when they find you legitimate and relevant. Your domain name registration depends on your extension and the sign up time, so be cautious while spending your money.
Make your site look relevant to your visitor. Avoid using other company's trademark and copyrights in your domain name. It is illegal to use copyrights and trademarks. Even if you get your keyword featured in other company's trademark, but you cannot use it as your domain name.
Search engines have a lost and found service for websites, if you have relevant domain then you are found and if you don't then you are lost. Your domain name registration requires consideration and appropriate research. Domain registration is easy but important to be done well.