FAM stands for Fertility Awareness Method. It is a natural way to prevent or induce conception. Many confuse it with the Rhythm Method, which any Catholic family would know is better for causing pregnancy than preventing it.
Rhythm Method works by taking the average days in a woman's cycle to produce a period of time in which the woman is most fertile. This method is not so accurate when it comes to a woman with irregular cycles, like me. My cycles are not that irregular, but I have been known to miss a month or be late by a few weeks several times a year.
FAM works by charting several indicators of fertility including BBT (Basal Body Temperature), Cervical Mucus (or also referred to as cervical fluid), and Cervix Position. This method helps a woman understand when ovulation has occurred, and by comparing previous months, helps them be better able to predict when ovulation will occur. The book, Taking Charge of Your Fertility is a great resource to getting into the world of FAM charting.
I started charting BBT the first month after we started TTC partially because of the delay that travelling caused. Every day I found it interesting to track what happened to my temperatures. I take my temp every day before getting up and it takes about 30 seconds. Easy. In fact it's helped me pinpoint that my luteal phase (or the later half of a woman's cycle) is longer than the average 14 days.