Shettles Method for Gender Selection
Just to be clear, I've never done this myself and I have no idea if it actually works. In theory, you can follow the shettles method to get pregnant with either a boy or a girl.
The theory states that male (Y) sperm are faster but more fragile than female (X) sperm. Also, X sperm does better in an acidic environment then Y sperm. The shettles method tries to control these things by timing intercourse and using different positions to improve your chances of having a boy or girl.
For a girl you should have sex 2½ to 3 days before ovulation and have shallow penetration so the sperm is deposited in a more acidic environment. Theoretically, the boy sperm will not survive long enough to get to ovulation and fertilize the egg. Only girl sperm will be left, therefore increasing your chances of a girl.
For a boy you should have sex as close to ovulation as possible with deep penetration. This way the Y sperm will be close to the "finish" line where their isn't much acidity so they'll be able to survive. Since the boy sperm is faster then the girl sperm the boys should reach the egg first and you'll get pregnant with a boy.
The theory is based on the idea that the human race needs more females then males to survive because females can only get pregnant so many times while males can impregnate hundreds of women if given the chance.
Again, I have no idea if this works. but if you want to try it, go right ahead! Let us know if it works for you :)