Summarize the following:
You can time your ovulation in many ways. The most accurate method is to use an ovulation predictor kit (OPK). If you have a regular menstrual cycle, you can also predict the date range of ovulation by counting back 12-16 days from the date your last period started, though the prediction might not be entirely accurate.  Keeping track of ovulation can also increase your likelihood of conceiving at all (regardless of sex) because women are usually the most fertile in the few days prior to ovulation.  Other signs of ovulation include abdominal pain, changes in vaginal fluids, and changes in basal body temperature.  Consider tracking your cycle carefully on a calendar in order to understand how your body responds to ovulation. Female sperm carry more genetic material, making them heavier and slower than male sperm. Having sex at least two days before ovulation gives the slower female sperm more time to move up the uterine canal before the egg arrives. This is known as the "Shettles Method." There is an alternate theory known as the "Whelan Method" that suggests that sex should take place 2-3 days prior to ovulation to conceive a girl and 4-6 days before ovulation to conceive a boy.

Summary:
Track your ovulation cycle. Have sex 2-4 days before ovulation to conceive a girl.