When I clicked this topic I expected something entirely different...hehe
Anyway, here's some general ways to distinguish male from female. Nothing's black and white and the only sure-fire way to know is to see them breeding...
General body shape - Female: round; Male: angular
Head shape - Female: flat, ski slope shaped; Male: forms a hump
Eye/Nose band - Female: flat, inline with forehead shape; Male: develops a ridge at maturity
Dorsals - Female: held slightly backward, in line with the forehead angle; Male: fully erect, forms almost a 90 degree angel with the head bump
Ventrals - Female: tends to hold ventrals closer to the body; Male: held erect, forming a distinct angle with the body
Lateral line - Female: nose tends to be slightly elevated compared to the tail; Male: nose and tail are fairly horizontal