1. Rules such as “.com only” for domain extensions are outdated today. The success of sites such as Del.icio.us, Bit.ly, etc. has meant that more and more people are okay with alternate extensions. If you can’t find your desired domain in the .com extension, by all means feel free to pick a more creative and “daring” extension.
2. Long or short, the length of your domain doesn’t really matter anymore. While past guides would cap the length at around 8 or 9 characters, nowadays, you can have the domain as long as you want, provided it conveys your site’s purpose and is easy to remember. Sites with long domains like ‘ICanHasCheezburger.com’ etc. have maintained popularity despite the twisted name. While you should try to get the shortest domain possible, if you feel that a longer domain would bear more marketing benefits, by all means, pick it.
3. Google, Digg, Scribd, Tumblr – these are examples of sites that have proven to be massively successful despite the apparent misspelling in their names (though Google is a bonafide dictionary word today). Creatively misspelled domain names can give you some powerful marketing horsepower. Not to mention that misspelled names are usually available while their correctly spelled counterparts may cost you thousands of dollars. So get creative and don’t hesitate to pick a name that might just not spell right.
4. Lastly, avoid hyphens in your domain name unless your keyword demands it, or when the domain would be difficult to read without it. Hyphens are an old fashioned way of picking domains and have no obvious benefit other than making your domain name more difficult to type. Avoid them at all costs.