You'll know the one when you see it and it's reaction to you is key!
I have had only males. Buddy is my first Yorkie and i have never had a dog
mark in my home! I give all of you credit for dealing with this problem because
I really don't think I could. I would think it is the dog not the sex that makes these problems. Marking, shyness, agressiveness etc. Buddy is a cuddle bug and has a strong personality. I have to convience him at times what I want him to do but he works with me. As far as I am concerned he is the perfect pet for me.
Good luck in your search and keep us posted when you bring your furbaby home.
Carol