Great thanks. The only thing I am confused how how to create canonical tags for your category pages. Anyone shed some light on this issue?
If you're trying to avoid duplicate content on an ecommerce site, canonical isn't going to help much.
Canonical is for when your ecommerce CMS (for instance, osCommerce) does something totally retarded and sticks the session ID in your URL, giving Google the impression that multiple versions of your product page exists (exactly the same).
Then the canonical might sometimes be used for categories. Never for tags. Tags will give you a bazillion duplicate content pages and there isn't anything you can do about it (except nofollow tags and noindex/follow tag pages), and canonical won't fix it. This is when you tag a product with 3 different tags and each of the pages those tags represent suddenly get a snippet, exactly identical, for that product. Canonical won't fix that.
Canonical won't fix categories when assigning a product to multiple categories.
Canonical WILL fix your category page when your category page happens to have various methods of sorting (sort by price highest to lowest, sort by price lowest to highest, sort by reviews, etc.), if your ecommerce CMS is retarded enough to index a different version of the category page for each method of sorting, but this shouldn't be common. Don't even bother with this unless you specifically see your category page for a certain product indexed with several variations of sorting.
Category pages are huge on duplicate content ... in fact they typically consist of nothing but duplicate content. You should either type a big unique intro to each of your category pages, or you should "noindex/follow" them. You want to noindex them when they are nothing but duplicate content ... but keep the follow.
Even though it is particularly difficult, I like to SEO category pages because its the category that represents the keyword I'm chasing after (I usually don't try too hard for product names). Either that or I make a big long post representing several products in that category where that page could technically almost qualify as a category page, and rank it for the category keyword.
Most CMS should handle canonicals presented by categories (most would nofollow the several methods of sorting so they shouldn't get indexed). Some (like osCommerce) are just plain stupid and stick the session ID in the URL thereby screwing up your product pages by making duplicates ... you need to focus on those.