You should read Taking Charge of your Fertility by Toni Weschler. It is very informative and will probably address all your questions. My husband and I have used charting as a method of birth control (slightly more involved than just taking your temperature) for 6 months. Last month was our first month "trying" and we conceived!!!
this website may also help you...
http://www.epigee.org/guide/nfpchart.html
good luck!!!
Melissa