The single most important thing you can do is to feed your dog healthy foods and treats.  There are some quality pet food resources listed here - some that even deliver directly to your door!

Click on the title to see their web page and service offerings.

Mud BayIf you've never walked into a Mud Bay store, you need to! They have an excellent and well trained staff who can guide you in selecting the best foods and treats for your pets. They have several locations in the area -- I love them!
Smiley Dog Smiley Dog is your Seattle neighborhood source for the best quality pet foods, toys, kitty litter and pet supplies. Smiley Dog specializes in healthy, natural dog and cat foods to support your pet's health and happiness. These folks have an impressive array of healthy and natural foods and treats. They currently deliver from Everett to Tukwila.
Reber RanchIf your don't live in S King County, Reber Ranch is still worth the drive. This is a farm supply store and you can buy everything from saddles for your horses to treats for your teacup poodle. The staff is wonderful and they have a great selection of foods, toys and treats for every pet's needs.