quick onsite SEO techniques to avoid duplicate content

1. redirect index.php to your main page

RewriteBase /
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.php\ HTTP/
RewriteRule ^index\.php$ http://www.yoursite.com/ [R=301,L]

2. use canonical tag properly, so for http://www.yoursite.com/my-list-of-products?orderby=name&orderway=desc you should have:

3. redirect non-www to www version
RewriteCond %{HTTP_HOST} ^yoursite.com [NC]
RewriteRule ^(.*)$ http://www.yoursite.com/$1 [L,R=301]