There is no natural method that can guarantee you will conceive a baby girl. Women always carry the X-chromosome in their eggs. Men carry both X-bearing (female) and Y-bearing (male) sperm. When X-bearing sperm penetrate the egg, the baby is a girl. If the Y-bearing sperm penetrate the egg, the baby is a boy. The books "How to Choose the Sex of Your Baby" by Dr. Landrum B. Shettles and "The Preconception Gender Diet" by Sally Langendoen explain how you can make your body a more favorable environment for X-chromosome sperm, thus increasing your chances of conceiving a daughter.
Identify when you ovulate. Mark your calendar when you begin your menstrual cycle each month, so you can see how long your cycles are. Count from the first day of your last period to the the first day of your current period for a few months to determine your cycle length. Purchase an ovulation predictor kit and use it about halfway between your cycles to determine exactly which days are your most fertile.
Have intercourse two or three days before you know ovulation will occur to allow the quicker-swimming but faster-dying Y-chromosome male sperm to die off. Do not have sex again until after ovulation. Since X-chromosome female sperm are slower but live longer, they will now have a chance to make it to the egg.
Douche with water and vinegar immediately before intercourse to create a more acidic environment, which favors female sperm. Use four parts water to one part vinegar. Have your partner take a hot bath immediately before intercourse to give the X-bearing sperms an advantage.
Avoid having an orgasm, to keep the vagina more acidic, as X-bearing sperm prefer an acidic environment. Avoid sexual positions that involve deep penetration, since the female sperm can make a long journey to the egg more easily than male sperm who die quickly. Try missionary position with shallow-penetration strategy to deposit sperm far from the cervical entrance.
Go on a diet that will alter your body's pH and influence your cervical mucus, thus making a more hospitable environment for female sperm and a less-welcoming diet for the male sperm. Eat foods high in calcium, like milk, yogurt, cheese, collard greens, broccoli and beans. Include plenty of foods that are high in magnesium, like artichokes, barley, almonds and spinach. Avoid foods that are high in sodium and potassium, as these will have a direct influence on the cervical mucus in the female. It is thought that cervical mucus is alkaline, and the diet can influence the ability of the swimming sperm and fertilization. If the food a woman eats reaches her cervical mucus, it is believed that it can help select the gender of an infant at the time of conception, though more studies are needed to provide a better understanding of the process.