I just buy mine at the grocery store and boil it up with a little bit of garlic. Although mine, as are most labs, are such chow hounds I can use anything and they will bait for it.
If I don't make my own, I buy Great Bait at the dog shows from a dog supply vendor.
Here is a link to Great Bait that you can order online: http://www.greatbait.com/
I actually make my own, and it's really easy to do.
I just get some calves' liver from the grocery store, lay it on a cookie sheet, coat it with some olive oil and some garlic powder, and bake it. The (fur)kids come running into the kitchen with their noses up in the air, wondering when the timer will go off! You can imagine how attentive they are in the ring when it comes out of my pocket!
Sprinkle w/ garlic powder, and simmer in a pan until no longer pink. Then put in a pre-heated and turned off oven for an hour on a cookie sheet covered with paper towels. Cut up and keep in ziploc baggie in freezer.
Cook liver in water on top of stove until done (4 min at most). Drain, cool and cut into small bite-size pieces. Put them on a lined baking sheet and place in cool oven (about 200) for around 2 hours, or until dried out. I also sprinkle them with garlic before putting them in the oven.
I should note my husband "sampled" these and said they were great...I told him he had to leave me enough to take to the show
Bowsers Best buffalo bites are the best bait i've found yet, the dogs love it and it's not too hard or too soft and it doesn't get all mushy like homemade liver and they don't get the runs from it, do a web search for the best price on it, trust me i've been through so many different types of bait in my many years of showing dogs and this one is tops.
Aloha,
Jackie