Pellets are labelled as either standard or premium. If it's a premium pellet it will have the word premium on the bag and is suppose to burn with less than 1% ash remaining. If the word premium is not on the package, it's standard fuel and is suppose to burn with less than 5% ash remaining.
The Pellet Fuels Institute ((broken link removed to http://www.pelletheat.org/2/index/index.html)) is the organization that sets the standard for pellet fuel quality, so if the fuel you are purchasing has the word premium AND the PFI logo on the bag, you can be pretty confident that it is a good quality pellet. Until there are stricter controls, that's what I look for in a pellet: Premium & PFI.
I have 3 tons of Barefoot pellets coming soon and if you look
here you'll see the Pellet Fuels Institute label on the bottom of their webpage.
Steve