Probably if you are physically delicate and 'feminine' looking you may only look androgynous by dressing as a man. I am small and fine-boned. Some people say I pass for male quite well, but I more often get the impresion that people find me eerily sexless-looking in my suits. I would rather look like a man in my suits and eerily sexless in androgynous clothes, but alas. If you are in this situation, foregoing the makeup and wearing androgynous or 'boyish' (but not distinctly masculine) clothing will not make you look androgynous, and may even make people believe that you are deeply at home with and confident in your femininity, and wearing only one earring will just make people inform you that you've lost the other one.
If you're fairly androgynous-looking to begin with, your milage will vary.
A waistcoat (vest) that buttons up fairly high and has a stiff front (a leather biker's one, or one from an old-fashionedish three-peice suit) can do a good job of making you look flat-chested, depending on what size you are. You can try a pair of women's support panty-hose, with the legs cut off for armholes and the crotch cut out for a neck hole. Put this on and then reach up under it and pull your breasts down and apart.
Try your long hair pulled back tightly and secured at the nape of your neck, not the back of your head. The effect will be better if you slick it back over your head, with pomade or summat. Or just water when you're trying it out for the mirror. You want to slick down all the little soft fringey bits, which are very feminizing.
