Personally, I prefer to have http://domain-name.com rather than http://www.domain-name.com
In fact, unless you specify that they are the same site, Google can treat them as seperate Websites, and you would be diluting your page rank!
So:
Connect to your website via FTP. Find your .htaccess file (usually in your public_html/www folder). If you can’t find one, just open your text editor (notepad will do) and save it as “.htaccess”.
Find some clear space, and type the following:
RewriteEngine On RewriteBase / RewriteCond %{HTTP_HOST} ^www.domain-name.com$ [NC] RewriteRule ^(.*)$ http://domain-name.com/$1 [R=301,L]
Simple? Yep!
Save & Upload! Sorted!
note: this is to UNIX-based machines only (UNIX is the most popular out there..)
Any questions just send me a direct message or leave a comment.