Complex sentence: Usually, the only way to find out how exactly people identify themselves is to ask them, and sometimes, transgender people either cannot or will not define themselves any more specifically than "transgender", "queer", or "genderqueer".
Split into simpler sentences: Usually, the only way to find out how exactly people identify themselves is to ask them. And, sometimes, transgender people either cannot or will not define themselves any more specifically than "transgender", "queer", or "genderqueer".