There are a few important rules for picking a URL:

1. It should be as short as possible.

2. It should be memorable.

3. It should NOT be a generic description of what you do. "Yahoo" or "Google" is better than "searchengine.com"

4. In almost all cases, ".com" is better than another TLD. Exceptions: Non-profit organizations (or businesses that want to look like one) should use ".org".

5. Don't use a variation on the URL you want because it isn't available. If "fredhouse.com" isn't available, don't use "fredhouse.net", "fred-house.com" or "myfredhouse.com". Why? You'll send traffic to the other site and confuse people.

6. In most cases, don't even bother trying to purchase the already-registered URL you want. The owner probably wants a ridiculous amount for it.

7. A good rule of thumb for any naming, not just URL: check and make sure it isn't easily distorted and made fun of. Names one sound different than an obscenity or something disgusting are a bad idea.

It's worthwhile spending a little time figuring this out. After all, you are going to live with that URL for a long time.