In order to get the most accurate reading when taking a basil body temperature as an ovulation predictor, most women prefer using a basil thermometer instead of a regular digital or mercury filled thermometer. Basil thermometers typically can measure to the 1/100th of a degree. Many of these thermometers also have memory storage, making it easier for you to compare other temperatures. Other features include beeping at peak temperatures and an ovulation chart for you to monitor your temperatures on a daily basis. Once you've established a pattern in your morning basil temperature, you'll need to look for the slightest elevation as an indication of ovulation.