A forest truffle is actually a mushroom, but an unusual one -- a mushroom that grows under the ground. That fact makes them especially difficult to find, because you can't see them. High-quality truffles in Italy and France often fetch hundreds of dollars - they are a culinary treasure that few can even truthfully admit to ever tasting. Truffles near equal to those from Europe can be found right here in the U.S., and while they are the world's most expensive single food ingredient, they can be found for free if you know where to look.
Rely on the help of forest critters. Voles, squirrels and chipmunks love truffles just as much as humans do, and if you look for evidence that they've been digging in a certain area, you just might find truffles nearby. Truffles, like other mushrooms, often grow in clusters quite close to each other -- so if you find one, you may find more in the near vicinity.
Search near trees. Truffles will always be found near a tree's roots. Specific types of truffles have an affinities for certain forest trees, but almost any tree can support truffles, although you aren't likely to find truffles under a maple and cedar. Douglas firs, pines and hemlocks are trees to pay close attention to.
Probe for truffles with your bare hand. When you find evidence that animals have disturbed the forest floor (small areas of pushed up earth and small holes in the duff), push your hand under the surrounding duff and, with your fingertips, feel around for a hard, ball-shaped object, generally the size of a walnut or a ping-pong ball. There may be only one or there may be several -- just keep feeling around the area. When you are done, pull the cover of duff back into place to leave the area as much like you found it as possible.
When you've found what you think is a truffle, smell it. If it's ripe and eatable, it should have a rich, earthy, garlicky, pungent smell (some think the aroma is wonderful, others think it's funky). However, you may not smell anything -- often, conditions in the woods are cold and wet during truffle season, and your truffle may need to warm up before it gives off its smell. Take it home and smell it again. If there's still not much smell, wrap it in a paper towel and put it in the fridge for a week or so -- often it'll ripen there; however, if it's just too young, it won't get any riper. Another way to determine if you have a real truffle is to cut it in half -- most of the eatable truffles noted have solid cores with unique, beautiful marbling throughout.
Use the truffle you've found -- especially if it has a rich, pungent smell -- to train your dog to find more truffles. Place the truffle in the toe of an old cotton sock, along with some other stuffing (some trainers like to use an old 35mm film canister instead). Use it to play "hide and seek" with your dog -- make sure you reinforce the smell by letting the dog smell the sock between each search. Use a command like "Get the truffle!" each time. Dogs like things that have pungent smells so your dog should enjoy the search. Remember to reward -- food and praise -- for each success, and make the search harder and harder, always using the command "Get the truffle!" Eventually, you can move the game outside, where you can bury the sock in the ground or under pine needles. Keep the sock in the fridge -- eventually it will get very ripe, but your dog will love it. Once your dog gets good at this game, take him out to the woods for the real thing. A good truffle dog is the answer to consistently finding plenty of ripe, eatable truffles.