As mentioned above, get up early and go listen, preferably before the season starts if you can. Turkeys will generally let you know where they roost by gobbling while still on the roost either before or right at first light. Once you get a general idea of where they are roosting you can inch a little closer and listen to see which direction they go once they fly down. Binoculars are invaluable in these situations, as getting too close can be detrimental in trying to establish a pattern of their movements after fly-down and throughout the day. I'd rather be 200 yards too far away than 10 yards too close. Good luck!