Make sure you set your definition of nuc ahead of time, everyone has their own idea of what a nuc should consist of. Make it known what your definition is up front and there will be fewer issues down the road. Get a deposit at ahead of time, make it know that it is non-refundable after a certain date. Be transparent on all the info about the bees, what treatments they have had, may need etc. The fewer suprises the better for everyone.
Pick on centralized spot for all your notes, orders, payments etx. and keep it accessible. I don't take orders if i am not prepared, call them back when in your office, whatever it takes.
Aaron