I run an ecommerce site that paginates product pages within Categories/Sub-Categories. Currently, products are not displayed in multiple categories but this will most likely happen as time goes on (in Clearance and Manufacturer Categories). I am unclear as to the proper implementation of Canonical tags and Rel=Next & Rel=Prev tags on paginated pages. I do not have a View All page to use as the Canonical URL so that is not an option. I want to avoid duplicate content issues down the road when products are displayed in multiple categories of the site and have Search Engines index paginated pages. My question is, should I use the Rel=Next & Rel=Prev tags on paginated pages as well as using Page One as the Canonical URL? Also, should I implement the Canonical tag on pages that are not yet paginated (only one page)?

I know that creating original product descriptions is best practices. What I don't understand is how other sites are able to generate significant traffic while still using duplicate product descriptions on all product pages. How are they not being penalized by Google?