Do you know the area well? Any ideas where they typically roost? Get within calling range of those areas, right before dark (or at dark) and hoot like a screech owl. You can often locate them this way, as owls are a natural predator and the males will gobble in response. Come set up within 2-300 yards in the morning, before light. At daylight, start calling (lonely hen) and listen - paying close attention to if the gobbler's getting closer, or going away. If he's going away, he's with a group of hen's that he's not leaving. Time to move.... It's a bit cat / mouse with a smart gobbler.
Also - unlike Texas deer hunting, you need to wear AMPLE camouflage. They are extremely good at pinpointing a location, and their eyesight is impeccable. Once they have you pegged, they will just run and you may not ever see or hear them. Try not to move much if you have a gobbler that is making his way into your area - become the tree / bush / background.
If he's getting close, don't over-call. Similar to ducks, you can over-do it.