Ready to have a baby? Experts agree that determining when you're ovulating is the single most important factor in getting pregnant quickly. But with so many methods out there — from charting your basal body temperature to using an ovulation predictor kit — where does a woman start?

The general rule of thumb is that women ovulate 14 days before their next period. A normal menstrual cycle will last between 23 and 35 days. (If your cycles are shorter or longer than the normal range, you might want to consult an expert.) But because a woman's body varies from month to month, few women have the exact same number of days in every cycle. And because sperm can live for two to three days after intercourse and the egg can survive for only 12 to 24 hours after ovulation, the optimal time to have intercourse is one to three days before ovulation. So here's the tricky part: How can you predict ovulation if your cycle changes every month?

Here's a breakdown of the most popular free and over-the-counter methods available to help you predict ovulation. Not every method works for every woman, so you might want to try a few to see which one is best for you.