The best way I have found, assuming you are in the USA, is to go to that state's DNR website. They will have a map with all public land and what can be harvested from that land. This I found to be the most helpful starting point for finding public land.
From there the most helpful person you can find would be a local DNR agent. They spend their time on the public land and are aware of the signs that a species is in abundance and if it is a good place to hunt.
Most regulars near public land will not be as helpful as you think because you are basically competing against them for the same resources. They might say oh try "blah blah" but they most likely won't tell you specific places. You would have better luck being friendly to a DNR field agent.
UPDATE: If you a specifically looking to pay for the land one of the best places to check is craigslist. When you do this a good question to ask is if you are going to be the only one hunting the land or if they are rent to multiple people on separate weekends. It may cost more the get it exclusively but the game you are hunting will be less pressured and you should then have better luck.