How do I determine if my lizard is a male or a female?

This depends on the species of lizard. A few species, such as the Western fence lizard, have different coloration depending on gender (the male has the blue belly which gives the species its popular name). However, with most lizard species it's more tricky than this and you need to look at the area beneath the tail. Male lizards often have femoral pores, which are bumps that run in a line down the inside of the thigh. Males also tend to be wider at the base of the tail - although this is difficult to recognize unless you have another lizard of the opposite gender to compare it with. Lastly, female lizards have paired scales near their cloaca, which are bigger than her regular scales.