I've heard that usualy lanky plants are male and bushy ones are female
however
I've had lanky plants become female and bushy one's turn out to be male. so i don't really buy into the theory. Personally i'd flower them and let them show me what they are. if you have males next to females remove them asap or they will pollinate your females and you'll get seedy buds. unless ofcourse you want to breed.