some misinformed people will say you can identify trans women by physical features you can see. this is not true! the real way to identify a trans woman is by getting them to talk about their hyperfixation of choice for an hour
trans women reading this going, "what! i don't have a hyperfixation": please, tell me more 
@chirpbirb ANYONE who doesn't have at least one hyperfixation worries me. Cis folks included.