There are differnet types and levles of mineral rights. It gets complicated, and sometimes the owners of the land have them and either don't realize it, or want to keep what they have. I always put in the contract that I want he owers mineral rights, and when it goes through title, they are transfered to me. It's how I have what I have on my land.
Also there is surface rights to get to the minerals below. It might not apply, but if it does, you can refuse any surface access to the minerals below, but still receive royalties if your land falls into the block of other properties that are included if they drill near you.
This is what I've done and have been able to make a buck when they are drilling close by, but not on my land. I refuse to give access on my land, but still get something for the lease of my mineral rights, and something if they find anything. So far, nothing profitable has been found, so it's not very likely that I'll make very much from what I have.
What's important is that I can keep them off of my land, and if you can figure out how to do that even if you don't have mineral rights, you might want to work that into the deal.
Good luck,
Eddie