OK, 30+ years experience on both sides of the counter........
Treat women as real customers, we control much of money in this country and are buying guns in record numbers. Also, you never know, she might know more about guns that you do.
Encourage newbies to ask questions, show how the gun operates, emphasize safety, training and practice.
A small (like J frame) double action only is not a good choice for a new shooter.
Shotguns: A .410 is not a good choice for a child or smaller woman, make it a 20ga and they can enjoy it for a lifetime.
Rifles, don't know a lot about them other than .22lr.
Know the hunting laws in your state, when and what firearms can be used.
Know your state and local laws regarding open carry, conceal carry, in the home, in your car, stand your ground and all that legalize.
Watch for signs of a straw purchase, you CAN deny a sale or transfer, I have done it.
Don't deal with drunks and druggies.
In the firearms business, the customer is not always right!