Generally speaking, the females are larger and more heavybodied than the males, if you have a mature male and female you'll see a noticeable difference.
Cories also prefer to be in shoals of five or more fish, they'll be happier and more likely to mate in larger groups. Breeding is commonly induced in many types by water temp changes simulating seasonal change in their natural enviroment, I believe, if I remember correctly that higher temps followed by heavy water changes with cooler water help induce spawning.
I would also recommend feeding of high protein and live foods if possible to condition the fish for spawning.
Its been quite awhile since I kept cories, so I may be slightly off base...
Anybody else here got more info???
Best you go over to Planetcatfish or a Corydoras specific forum perhaps.
