At the end of menstruation, the fluid will become sticky and then possibly creamy and white. As you near ovulation, the fluids will become clear in color and stretchy, resembling raw eggwhites. This is your most fertile time. According to Toni Weschler, the last day of the eggwhite fluids is the most fertile day of the cycle. After ovulation the cervical fluids dry up considerably, becoming sticky again, and often yellowish.
Some women notice their fluids become more watery a few days before menstruation.
This is caused by the breakdown of the uterine lining. Another characteristic of fertile cervical fluid is its appearance under a microscope. A smear of cervical fluids during your most fertile time should look like ferns, similar to frost on a window pane. Incontech sells a miniature microscope which looks like a lipstick for the purpose of predicting ovulation through the observation of ferning. You could also use a simple child's microscope.