It's all about confidence. Or accepting the fact that you don't have to apologise for the fact that you exist and just going with the fact of being a woman - after all we come in many varieties.
I'll tell you a funny story, which is both life affirming and life changing in a minute. But for the time being let's concentrate on people watching. We notice unusual people and pay them greater attention. Over time I've seen the odd woman who caused me to think "is she?". Don't hate me for doing that, I've already hated myself for thinking it, but the reason was generally something about behaviour rather than appearance. In all cases there was something on the edge of my perception. What to call it? Furtiveness? Perhaps being withdrawn. It's weird - when we actively try and deflect attention from ourselves we quite often end up attracting it. Which leads to the opposite. What of the dozens, hundreds maybe of trans women I've seen or spoken to or otherwise fleetingly encountered who haven't registered at all? What did they do? The answer is nothing more than present as comfortable in their own identities.
We attach credence to something called 'Expert Power' in sociological terms. Usually it's used to describe the phenomenon where we tend to believe the expert when they tell us something, or give information concerning a topic we know little about. We make the assumption they know the answer, or their opinion is somehow correct, based on our perception of them and the overall power relationship.
Which is something we can use to our advantage. Or at least I've tried it and it seems to work. Simply put, be the 'expert' when presenting gender to someone who hasn't yet formed an impression. As long as it's done with enough confidence, other people are less likely to question and more likely to distrust any contrary cues. If nothing about your manner suggests doubt in the fact that you are female, then it's less likely to translate into doubt in others' minds. I don't have to full on say "Hi, I'm a girl" - but I can work on various ways of implying it. If this sounds daunting, it is. I was terrified the first time I went out!
Now for the funny story. This was my first time out in London (I don't live there, only kind of near it). I'd gone up on a Saturday in order to meet someone and was dressed for a semi-smart occasion: black trousers, ballerinas, blue blouse and a black jacket. Plus a little makeup and some jewellery. Anyway I needed to cross one of the large parks in the middle of the city. Went in and, in usual ditzy style, paid no attention at all to my surroundings. Which was working fine until I realised I had wandered in to the middle of a women-only, national level charity running race. Lots of people were walking, as it was near the end and it's generally for amateur entrants. So that part wasn't a problem. What was, kind of, was finding myself in the middle of a crowd of several thousand women in pink themed fancy dress. On a route past even larger numbers of spectators.
Did anyone care? Of course not, nobody even noticed I was there. I was eventually ejected by a marshal as I didn't have the relevant race number! I had attempted to leave the course after realising I shouldn't be on it but there were barriers everywhere. Quite why there wasn't one at the point I stumbled in to the race I have no idea. Never mind.
What was, simply, life changing about that was the overwhelming impression that nobody was at all bothered. I know it's more difficult in a small town and perhaps in other, more conservative places. But I think it served to highlight the fact that most people care about themselves, their families and their friends. Not what some random person on the other side of the street is doing. So use that to your advantage and let them get on with it! They don't really want to think about you, so let them carry on with their solipsism. It's so difficult at first, but once you've gone through the initial difficult phase then being in public shifts from being oppressive to liberating. I'm not going to lie though - gatecrashing a running race possibly isn't the best place to start!!!
