Temps tend to be lower in the follicular phase of your cycle (from the first day of your period until ovulation). Some people see a dip just prior to ovulation, but that's not super helpful because your temperature naturally fluctuates a bit and you may not see that dip before you O anyway. You can tell you've ovulated after your temps have risen and stay high. Temps tend to stay high during the luteal phase until

If your temps stay high for longer than your usual luteal phase and the witch doesn't make an appearance, you have good reason to POAS.
This is a simplified explanation, but the best thing you can do is start charting (things make so much more sense once you see the pattern in your own chart). Fertility friend is free and offers great lessons to help you get started. Good luck!!