The shettles method, where you plan intercouse to conceive a certain sex isn't fool proof, obviously. I had sex every other day and even on the day I ovulated and I conceived a girl. This pregnancy, we did the same thing, just going with the flow, and I conceived a boy.
I had sex on ovulation day and the day after and I'm having a girl, so pretty sure its just luck of the draw! :)
Some people say to have sex a few days before your ovulation day because male sperm swim faster, but don't live as long, and female will last longer, and it gives the male sperm time to die off quicker, I'm sure it's not 100% true, or fool proof.