Ben, This can be so important now I'd advise speaking to a board certified real estate attorney about it. If you are working with a realtor, most of the larger offices have mineral rights reservation forms prepared by their attorneys as part of their contract packages. You might be able to ask a title company for a clause as well, but they may be hesitant to give out, but doesn't hurt to ask. They may do it to get the deal. If you really value the mineral rights, don't resort to Office Max forms. They may work, but you might pay for it later if they don't. Angelia's answer is a good start, but to me this is nothing you want to fool around with.