As a trans person who's run the gamut from early youth outings to where I am now, I can almost tell what people are thinking by the kind of looks I have gotten over the years. In the early days, I might get the sly smirk or the beady eyed stare which signified I had been read as an imposter. That was before I had any self confidence and would carry myself as a terrified husk of a person.
Today I know I am mostly being read as a cis woman or sometimes perhaps a transitioned trans person just by the stark contrast of change in the looks I get; or perhaps I should say the lack thereof.What has changed? Well mostly it's about exuding confidence that you know who you are on the inside. Yes, there was some work on voice, mannerisms, gesturing and so forth but once I permitted myself to indulge in these changes, they came fairly effortlessly and naturally. What was underneath the surface was allowed to be seen.
The other important aspect is not caring one whit whether you are being looked at. Always thinking that it's because you've been read is perhaps a mistake and I've had many women come up to me and tell me they wish they were my height and so, I no longer assume anything.