The simple way is to make sure they are sexually mature and then after cooling them for a few weeks over the winter feed them both well. They will go into a shed cycle after hibernation. When the female sheds, she should be ready to breed (sometimes this occurs after the first shed, sometimes after the second shed).
One way to know is to watch the male. If he is in the same room with her, he will be going nuts. He will be crawling around his cage very actively and may even refuse to feed. This means he smells her pheromones.
When this happens, carefully put the male in the female's cage (if the wet shed is still in there, it sometimes helps). He will immediately start looking for her and making jerky motions. She will respond by raising up her tail slightly. If they don't respond this way, it means they aren't in breeding mode.
I usually watch them for a few minutes to make sure they each understand the other intentions and aren't in feeding mode. If they seem to be going through the courtship (her crawling with him trying the get on top of her and rubbing his chin on her), you can safely leave them for a few hours. If they don't figure it out, better separate them and try again later.
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Chris Harrison
San Antonio, Texas