Without coming off as either a gender swapped version of a character (with no differences other than its gender), or being overly feminine/masculine?
For example i am currently playing a female mage in a fantasy RPG. However i am told that i dont come across as feminine at all, especially when i take charge and try to get the party on track. This is especially true when i talk, since obviously the way i construct sentences is masculine and not feminine. My character feels like it would be exactly the same if her gender was male.
On the flip side when i see females play male characters, they generally either come across as really feminine and passive, or they try to be overly masculine (playing something akin to conan the barbarian for example) to the point where it feels like they are trying too hard (hitting on every woman they see, bragging, stereotypical male behaviour)