There is one very important thing to always remember when looking to buy truffles: winter is the peak of the truffle season. So no matter what they say, a truffle will be at its best, and most flavorful during the winter harvest, which typically goes from October to March and peaks December to January. Also, you must remember that weather conditions change depending on the year and the geographic location, so there are other factors that affect truffle harvests, like an unusually warm winter, or an early spring.
Truffles are categorized according to color - black or white - and season — winter or summer- but you will also find other categories relating to origin, such as Italian or French truffles, which you should really ignore, as it really does not make a difference in flavor or quality (unless its categorized “Asian” in which case it indicates a different species of mushroom altogether- see our Chinese Truffles Section).
Within every seasonal and color category, you will also find grades, marks of quality that will typically indicate price and availability. One important detail to remember is that bigger truffles
fetch bigger prices because truffles are priced by weight, not size. So, a bigger truffle will be heavier, and therefore cost more. Size does not affect the flavor, aroma or quality of truffles.
The best, largest truffles, almost the size of a grapefruit. Very rare to find, and very expensive.
Oblong truffles about the size of ping-pong balls that are popularly used at restaurants. Constitute about ten percent of the crops and are fairly expensive.
The ones you'll most commonly be able to find (and afford), these are the lower grade truffles. They vary in size, typically about the size of large berries.