There's a company based out of Seattle that specializes in truffle dog training. I would highly recommend that if you want the quickest path to truffles. They're incredibly good and highly knowledgeable about dogs and truffles. (Not sure on the sub rules so I don't want to give out their name directly- but they're usually the top search result when you look for truffle dog training in the US)

However if you're looking for a cheaper alternative, first step is to get your hands on one of these truffles. Store it in your freezer and just use a little sliver at a time when training your dog. At the start, I just shove the scent infront of the dogs nose and say "Truffle" and then reward it. After that 5-10 times, move the scent a foot away, say "truffle" and reward the dog when they touch their nose to the scent. From there, just continue building up the distance from the dogs nose when you say "Truffle".

Both of my dogs, I trained them in my own house (hiding under carpets or difficult to reach places). Once they could go find 3 or 4 scents that I'd hidden in places around my house, then I took them out to the woods in areas that I thought looked promising for truffles. Think "Overgrown Christmas Tree Farm" but more specifically, Douglas Firs 10-30 years old (about 8-15 inches in diameter) and without too much understory growth.

Truffles leave behind a darkened patch of soil as they decay organic matter. The french call this "Brule Terra" meaning Burnt Earth, because it looks like someone took a torch around the base of a tree. It takes a little bit getting used to, but once you see it, you see it all over the place in Seattle. Especially if there's little craters around the base of that same tree, those craters are from squirrels and voles that have been digging up these truffles and eating them.

I've also heard that owls like to eat these squirrels and voles, so areas around an Owls nest, if you find one, are also highly likely for truffles to be present.