This VIDEO is from the Fleased Forum on Gas Lease Termination, held in Norwich, NY on March 14, 2013.  It is rather long, but very informative.  The presentation by attorney Joe Heath on Gas Lease Termination starts at the 34:34 mark.  The first 20 minutes or so of his presentation gives background information on the leasing practices of the gas industry.  Starting at the 56:35 mark, he focuses on the standard industry lease used in New York State.  He describes the issues in terminating such a lease and the steps that must be taken.
Fleased is an organization dedicated to providing a voice for fellow landholders who leased mineral rights before we knew that shale gas exploitation threatened our land, air, water, and communities.  They have a one page document on Gas Lease Termination.  They also have a more detailed document on How to Terminate a Gas Lease in New York State.