*No trustworthy scientific methods were used when compiling the results of this study. The evidence described below is purely subjective.
Potty training a boy:
At the age of two, take away the diaper.
Buy him underwear of his choice in hopes he will not want to soil it. Give up that hope twenty minutes later. Lock yourselves in the house for an extended weekend. Set up a potty in every room. Watch him pee on the carpet while standing right next to it for the next month or two. Buy a children's potty seat that goes on the regular toilet bowl so he can feel more like Mom and Dad. Realize quickly it was a waste of money, just like 90% of purchases related to kids.
Buy books. Books for him about how to go tinkle tinkle toot and books for yourself about how you are raising an emotionally disturbed sociopath as a result of your pressure (well, OK, maybe you don't have to sit on the potty if you don't want to...) or how you are raising an incompetent indecisive adult who will still live with you at the age of 45 as a result of the lack of the pressure (get back on that potty now!)
Start giving him Skittles as a bribe to go at least in the direction of the potty. Start giving him M&M's as a reward for sitting on the potty. Start giving him ice cream for dinner as a reward for actually going in the potty.
Stock up on laundry detergent and carpet cleaner. Don't fuss too much when he pees on a cat. After two or three months you will finally see some progress. Don't get fooled. Two days later, you will be hit by a tsunami of pee and poop as the little angel decides to regress. Go ahead and stuff your face with the remaining M&M's and wash them down with vodka.
About half a year later he successfully makes it to the bathroom at least six times out of ten. He insists that you keep him company at every bathroom visit, but that's a small prize to pay (until you realize, three years later, that it most probably won't stop. Ever. Even when he's 45 and still living with you.)
You consider him potty trained. Ta-dah!
Potty training a girl:
At the age of two, she takes away the diaper. She goes on the toilet. She tells you to get out of the bathroom and takes care of everything herself. The end.