Your cervical fluid gets more watery, stretchy and clear as you near ovulation. When it is most stretchy and clear, you are most fertile. If you are trying to achieve pregnancy, you should have intercourse when this kind of fluid is present because it indicates that ovulation is approaching.
After the most fertile stage fluid usually becomes more opaque, thick and creamy.
Cervical fluid can dry up a day or two before, or the day of ovulation or even the day after ovulation, so it is unreliable to use it solely as a way to pinpoint ovulation, though it is a great indicator of fertility.