There's a very good book available for those of us looking at dragonflies and damselflies in Texas. The photographs are clear; alternate color patterns of females are shown; the text for each species has a recent range map and discussion of habitat, etc.

Here's a reference to the book (1)

Male dragonflies have a three-parted clasper at the tip of their abdomens which they use to grasp females during mating. They also have, underneath the 2nd and 3rd abdominal segments, their secondary genitalia, called the hamulus. Little jointed finger-like tools reside inside of a small slot.
Segments 2-3 in the females are more rotund and swollen-looking. They often have clasper-like appendages at the tip of the abdomen, but they number 2 instead of 3 and are often shorter than the males'.
Many species are sexually dimorphic, meaning the males and females look different. Get a male and female of the same species (an easy species where the genders look different) and then compare the features listed above.

Good luck and keep at it!

Kurt Mead

A Glider. I think I can just make out the spots on the hindwing which would make it the Spot-winged Glider.