Eat a Girly Diet
Some gender-prediction mavens say that following a specific diet for a few weeks before conceiving could increase your chances of having a girl. They say that switching your diet changes the pH balance in your body, which some believe contributes to the sex of your baby.
According to this school of thought, the key to conceiving a girl is eating plenty of highly acidic foods, such as grapefruit, oranges, lemons, and so forth. The theory is that an acidic environment kills male-producing sperm, so female-producing sperm have a better chance of making it to the egg. Believers in this theory say your diet also should be high in calcium and magnesium but low in salt and potassium if you want to conceive a girl.
(Of note, an acidifying diet is not necessarily made up of acidic foods (but often, rather, junk food), and is considered by some researchers to be a not very healthy diet. See The pH Diet and Your Fertility for more details. Meanwhile, however you modify it, BabyZone sticks to its guns on urging a healthy and balanced diet in pursuit of conception, period.)