I have always sent mine to my sheriff along with a short letter like this:
FFL Letter to Sheriff
April 10th, 2013
Ulster County Sheriff’s Dept
Ulster County Law Enforcement Center
Kingston, NY 12401
Dear Sheriff Van Blarcum,
This notice is to inform you that I have submitted my renewal application to the ATF for my C&R Collectors license and I am providing a copy to you. This requires no action on your part as it is standard ATF policy that I inform your office. I have had a C&R collectors license for over 13 years now, I do not run a gun business of any kind out of my home I am a private collector.