My girlfriend swears by this method. She wanted to have a girl first so she BD'd before ovulation and had a girl. Then she wanted a boy so she BD's around the time of ovulation and she had a boy. The she decided that she wanted another boy and BD'd again around ovulation and had another boy.

She also said if you want a boy you are supposed to have an orgasm and for a girl you are not. She got exactly what she wanted three times in a row.