Mostly it just came from ... living, I guess. Enough years (and it was a few *years*) of never getting clocked, and I started to settle down into having a boring average life.
Voice is a huge deal, it's true. I found that if I managed a very feminine voice and had long hair people would overlook a lot of other masculine cues. I don't have a trick for how I got the voice right, though; I practiced for literally hundreds of hours, recording my voice over and over and trying to repeat what worked, plus I imitated women I liked. I'm a pretty good mimic, so that helped.
I was 5'8" too (I'm 5'7" now), but women around here have an average height of more like 5'5", so it doesn't stand out. Still, even 5-6" taller than average isn't going to out you by itself, and confidence [even faked] counts for a lot.