One of the easiest ways to gain insight into your reproductive health is through basal body temperature charting. BBT Charting, as it is called, is very easy to do. Every morning as soon as you wake up, before getting out of bed or moving take your temperature with a special basal body thermometer, found at any drug store or online. Record this temperature every morning at the same time. As you record and chart this temperature you will notice your cycles have a temperature pattern. Right after menstruation the temperature is low, then upon ovulation there is a temperature shift that increases for the remainder of the cycle.
Along with Recording your BBT, you will get more accurate results by recording your cervical mucus. Cervical mucus (or CM) will also change according to your cycle.
You can use a simple paper graph like this one or you can use an online charting tool like FertilityFriend.com or iVillage's Fertility Planner. The online tools will do the calculation for you. Whatever method you choose, I highly recommend the book Taking Charge of Your Fertility. This book will give you all the details about BBT charting.