Four things to think about.
1. Type the address on an iPhone or Droid. How easy is it to punch in? Are there special characters? Do you need more than one keyboard?
2. Verbally tell a stranger to go to your domain. Can they understand the spelling?
3. This ties in with point 1 – How many words is your domain? As few characters as possible is best, but especially words. 2 longer words are better than 5 short words, assuming the character count is the same.
4. Is Google flooded with the keywords in your domain? What about making up a word. Therefor you already own the Google search for your name.
Update: See #5 in the comments.
6. Buy your own domain name! Never let a web design company or agency buy a domain for you. I’ve run into dozens of small businesses that have no idea where their domain was bought or who bought it. What happens if the domain expires? What happens if that agency goes out of business? Own your domain.