There are many ways to determine when you ovulate. The simplest and most inexpensive way is to take your basal temperature every morning and record it on a chart. A difference in ovulation temperature might not be detectable on a regular thermometer, but a basal thermometer has concentrated temperature ranges immediately below and above normal temperature. This way you can track slight changes in temperature throughout the month. Chart your temperature daily. When you ovulate, you should notice a slight increase in your basal temperature. Some things like headaches or illness can affect your basal temperature. You can purchase a basal thermometer at most stores. Other methods of ovulation prediction include monitoring the discharge and position of the cervix. You can also purchase an ovulation prediction kit over the counter at most pharmacies.