Many women have had success using ovulation predictor kits , which are handy because they tip you off before you ovulate. This thermometer shows the minute incremental degree changes that a regular one can't.
Most basal thermometers come with a temperature plotting chart.
Make some extra copies of the chart in case it takes you a few months to get pregnant. Your BBT probably ranges from 97.2 to about 97.7 degrees before ovulation. During the two or three days after you ovulate, hormonal changes have caused a rise in your BBT of between 0.5 and 1.6 degrees, which lasts at least until your next period. You'll probably notice your temperature spiking on other days, but unless it stays that way, you probably haven't yet ovulated. If you become pregnant, your temperature will stay elevated throughout your pregnancy.