Better to ask what doesn't make me feel femme. I'll take the question along the lines of what things make me feel best / most feminine.
Being accepted by others as female, especially interacting with women, the more intimate, the better. This just doesn't happen so far with men, even those few who feel accepting clearly at some level just don't get it.
Full body contact hugs, feeling pressure of another woman's breasts, abdomen, thighs against mine ... strong and secure women do this, not the lean-in hug where only shoulders touch. Of course I experienced this with some women before my GCS and of course it's different now because my body feels more right.
Talking yes and even more, the truly face-face body language women use when we interact. Where men face each other it's most often obliquely and with less eye contact. Of course eye contact. None of this was easy for me before, being in the Asperger's realm of the autism spectrum, eye contact never felt natural to me and getting to a more comfortable place in how I communicate is key to that.
Also the less intimate interactions can feel so good about expressing a femme affect. More than a few times on the bus I've noted a woman (usually older) take in my appearance with some initial surprise ... femme attire and hair along with my beard and still fairly bald head ... What's wonderful is to see that woman then assess me up and down and smile, give me a quiet nod (always the eye contact). That little interaction says to me that she's seem what I have to work with, taseful attire etc and bingo, has accepted me as one of the group. Younger women in my area are more likely to just smile and nod, skipping the appraisal step.
And then there are the things I do to get that look: simply dressing femme, most of my underwear is pretty, of course nobody knows this but me and my few lovers. My skirts are simple and serviceable, when I wear makeup it's only visible in that aiming to brighten my features a bit and soften some of the masculine lines. I love wearing perfume and was quite self conscious about it until recently when I checked in with a friend after we'd been out at a crowded lesbian venue and she said it hadn't been obtrusive (she hadn't realized I was wearing any).
All of those physical / sensual things simply serve the purpose of making the communication easier. If I'm feeling femme and being read as femme then I simply feel more confident and presentation is a part of that. The fact that it's a social construct doesn't render it less real :-).
