If I were going to prepare my own dog food, I would educate myself extensively first. Two reputable sources of information IMO are:
Monica Segal (K9 Kitchen, as BCSnob mentioned above) and
Sabine ContrerasThey are two of the sanest and most accessible voices in the home-prepared pet diets realm. Monica Segal operates the K9 Kitchen Yahoo group
(here), and Sabine Contreras operates the K9 Nutrition Yahoo group
(here).
Both have certifications in Animal Health Care through the University of Guelph, one of Canada's top universities. Their Yahoo groups are well-moderated by very knowledgeable people. There's a wealth of info available on those groups.
Another very reliable source, although perhaps not quite so easily accessible, is
PetDiets, which is a service offered by Dr. Rebecca Remillard. She is a board certified veterinary nutritionist who currently teaches at the N.C. State vet school.
On this page of PetDiets you can purchase, for a very reasonable fee IMO, a balanced home-made recipe for dogs of various sizes. Note those recipes are only for healthy adult dogs.
Edited to add: I was clicking around on the NCSU vet school site and found another resource for balanced home-made pet diets. It's a bit spendy at $231, but knowing you're feeding your pet well would be priceless.
Nutrition service (click on "Owner Nutrition Consult Request").