15 SEO Best Practices for Structuring URLs

#1: Whenever possible, use a single domain & subdomain

#2: The more readable by human beings, the better

#3: Keywords in URLs: still a good thing

#4: Multiple URLs serving the same content? Canonicalize 'em!

#5: Exclude dynamic parameters when possible

#6: Shorter > longer

#7: Match URLs to titles most of the time (when it makes sense)

#8: Including stop words isn't necessary

#9: Remove/control for unwieldy punctuation characters

#10: Limit redirection hops to two or fewer

#11: Fewer folders is generally better

#12: Avoid hashes in URLs that create separate/unique content

#13: Be wary of case sensitivity

#14: Hyphens and underscores are preferred word separators

#15: Keyword stuffing and repetition are pointless and make your site look spammy

See details at http://moz.com/blog/15-seo-best-practices-for-structuring-urls