There is an old adage in the SEO world that one should never leave it up to Google to decide which page of your website to index. Matt Cutts uses the following four examples
here in his discussion about canonical issues.
www.example.com
example.com/
www.example.com/index.html
example.com/home.asp
But this post is about more than just singular domain canonical issues. Take the
Capone Photography Website for example. Many smaller companies, particularly in the photograhpy industry, are usually start-ups with little to no SEO knowledge and/or experience. SERPS for photographers like the Capones are merely a guess. But all websites, big or small, should take the guesswork out of domain usage. Capone Photography, for example, has one web site, but four domains. The domain they use in marketing pieces is not the domain that is indexed and ranking best right now, which creates an obvious problem.
www.caponephotography.com
caponephotography.com
www.caponephotography.net
caponephotography.net
As far as Google is concened, the right way to go here is to use a
permanent 301 redirect to point the .net version to the .com version. A 301 redirect can also be done to point the non-www version to the www version. An eaiser way would be to tell Google which version you prefer in your Google Webmaster Tools account. This yon't help your cause on Yahoo or MSN unfortunately. 301 recdirects are always the way to go; they are search friendly and pass along any links and reputation to the new domain. Good luck and email me with any questions you may have.