Here's what I would do: visit rock shops, starting in your area. See what they're offering. If anyone has the local petrified wood, what do the BEST specimens look like? How are they prepared (cut, polished, etc.)? How big and what price? Then go back, take a good look at what you have, and see if your material measures up. Do this before you have a serious discussion with anyone. Depending on what you find, the next people to talk to would range widely, from local rockhounds to mineral dealers to nearby college instructors to museums. There's more you can learn through the resources on the Rock Collecting list.
If you get serious interest, have an idea of the deal you want. Would you rather do the digging and delivering yourself or let someone onto the property to do it? Another possibility is opening your property to diggers, perhaps organized rockhound groups or even the public. Look at your logistics: maybe you're well situated near a city and could reach a large market—or you could open an online selling account instead. For this sort of planning, you'll find a lot of help in the About Business channel.
But maybe your stuff isn't marketable. Maybe it's just interesting. If there's no possibility of money, there are still good uses for interesting stuff—see if school classes would like the opportunity to learn about fossils and geology. After all is said and done, that might be the most rewarding use for your treasure, because the odds are slim that you're sitting on a fortune.
