Some people can sex them just by looking, but i'm not one of them afraid.
Its difficult until they get to around three inches long. The males get breeding tubercles or sometimes called stars on the gill plates and these spread to the front pectoral fins. Its been confused with ich but these are more bumpy looking.
The female has a vent that faces outwards and the male is inwards. Apart from that then only they know.
To breed them then you would need quite a long tank and lots of plants for the male to drive the female into and the temperatures must be low for a couple of months and then rise to simulate spring.