If you can, buy the dot-com version of your domain name, since that is the first url anyone will think of. If you cannot get that, buy another major domain type, such as dot-org. Buying multiple domains with the major domain types can also bring in more site traffic.
Do not use another country's ending, or you may end up losing your entire domain without warning. This has happened.
Note: the InterNIC has come up with a new ending, dot-name, for names—it can only be used for names. The name can be your name, a pseudonym, or a fictional name that you own rights to.