There are 3 major methods of predicting your most fertile times, short of purchasing commercial ovulation predictor kits. These methods include charting your basal body temperature charting (BBT), observing your cervical fluid, and observing the position and properties of the cervix itself. Many women find that one or two of these methods are very accurate, while another is simply confusing and frustrating. It is not necessary to use all 3 methods. In fact it is far preferable to use only the methods that give you the clearest result, and leave the others alone to avoid confusion.
You may have other signs of ovulation as well. These may include mittelschmirtz (a pain on one side of the abdomen caused by the follicle rupturing and releasing the egg), breast tenderness, the condition of the skin, and increased sex drive. Some women will find these to be highly accurate indications of ovulation, while others will not experience them at all.
How to interpret your BBT:
Your BBT is a good tool to use after the fact. By looking at a whole month's BBT chart you can tell when and if you ovulated. However, you cannot necessarily predict ovulation with your current month's BBT. Only by review of previous months BBT experience can you speculate ovulation for the current month.
Once you have completed a normal cycle, your BBT should show a distinct shift upwards, by about .5 degrees, 11-17 days prior to your period beginning. What happened is this: Once ovulation occurs (typically 11-17 days prior to the end of your cycle), the progesterone released causes a rise in your body temperature, usually the day following ovulation. The progesterone stays in your system for 11-14 days and then drops if the egg has not been fertilized. Therefore, the day your period begins will have a decline in your BBT. If an egg is fertilized however, the BBT will remain high as your body continues to produce progesterone. If you have high temperatures for 18 consecutive days, you can be pretty sure that you are pregnant.
Some individuals show a third rise in BBT if an egg is fertilized. This third rise occurs about 6-8 days following ovulation. This is when a fertilized egg implants into the uterine lining which causes another surge of progesterone.
Cervical Position
Another way you can predict ovulation is to observe the position and other characteristics of your cervix. Like charting your cervical fluids, this will take some practice. The cervix is located at the top of the vagina. You can reach in with your finger and judge the height, softness, and the size of the opening. Be consistent with the position you are in when you do this and the time of day. As you approach ovulation your cervix will rise, soften, and the opening will widen. After ovulation the cervix becomes lower and begins to harden again. This may happen gradually after ovulation, or the cervix may stay high until immediately before menstruation and drop all at once. Immediately prior to menstruation, the cervix should be very low, hard, and rather pointed. Don't ask what the cervix feels like in the early days of pregnancy, as there has been no consistent answer to this question. As with so many other things this seems to be totally individual. | 
