"Many women don't know the most fertile time in their menstrual cycle," says Victoria Jennings, Ph.D., director of Georgetown University's Institute for Reproductive Health. "Most think it's day 14, but ovulation doesn't always occur on the same day. It moves around, even in the same woman." Jennings says a normal woman's potential fertile days are days 8 through 19 of her cycle. (For a glow-in-the-dark bracelet to help you track when you're most fertile, go to cyclebeads.com.)
Then you need to have intercourse at least every other day during this time frame. "Having intercourse regularly, about three times a week, is enough," says reproductive endocrinologist Bill Meyer, M.D. But if you do want to keep closer track of when (or even if) you're ovulating, simple methods that can help include using ovulation-predictor kits, charting your basal body temperature and checking your cervical mucus.
For detailed information on these and other techniques, see Taking Charge of Your Fertility, by Toni Weschler, M.P.H. (Quill).