Hi James!
I normally advise people to not sell their minerals, but have come to recognize that sometimes circumstances make it necessary or desirable.
As far as procedures, first you need to find a Suitable Buyer. There are hundreds of companies and individuals out there that will be happy to make you an offer, but many will try and "low ball" you into accepting a lower price than a more legitimate Buyer would offer you. Some will try and buy your interests only to "flip" them to an End Buyer for a profit.
Once you have found a Suitable Buyer, that Buyer will present you with either a Letter of Intent (LOI) or a Purchase-Sale Agreement (PSA) setting out the agreed upon terms of the sale and setting a Closing Date.
The Closing Date will be far enough in the future to allow the Buyer time to check the title to your interests. It is the Buyer's responsibility to do so.
If there are any title issues that need to be cleared up before the conveyance can be completed, the Buyer will have a certain number of days to inform you of those issues and you will have a certain number of days to correct or "cure" those title issues before the closing can proceed.
If there are a number of properties involved, sometimes the Closing Dates are staggered to allow the Buyer to have time to check and clear the various titles.
There will be a certain amount of money, a few percentage points of the total sale price (5% or so), that the Buyer will pay you or place in escrow with an agreed upon Attorney or Title Company to hold the property while they check title. That sum is typically applied to the total sales price in any successful closing. Sometimes it is non-refundable if the Buyer backs withdraws their offer for any reason other than title failure.
Beyond all that, you just agree upon a selling price and sign the Mineral Deed.
I have successfully assisted a number of people who have met me through The Forum sell their minerals, not only helping them locate reputable Buyers, but also finding them greater sales prices than they had previously been offered.
If you need additional assistance, accept my invitation to become "A Friend" on The Forum and I will be happy to discuss that with you privately.
Hope this helps -
Charles Emery Tooke III
Certified Professional Landman
Fort Worth, Texas