Tracking your basal body temperature (BBT) can help pinpoint your ovulation date, and thus the best time to have sex. Take your BBT with a basal thermometer (sold at drugstores) first thing in the morning, before you do anything. This gives the most accurate reading — even a quick bathroom dash can raise your body's core temp. Keep the thermometer on your bedside table along with a notebook to keep a daily record.
In the first two weeks of your cycle, before ovulation, BBT averages between 97.2 and 97.6 degrees. A day or two after ovulation, your body temp spikes between half a degree and a degree, and remains elevated until your next cycle begins. Keep in mind that from day to day, your BBT can fluctuate by half a degree or more. Don't be fooled by a little blip — look for a sustained rise to confirm that you've ovulated.
The downside of BBT is that it shows when ovulation is over, not imminent. Track it for several months, though, and the info will give a sense of when you usually ovulate... Now just plan your sex lifeaccordingly!