1. Is the piece of clothing commonly worn by both men and women? The answer should be "yes".
2. Does the piece of clothing make you look particularly masculine or feminine? The answer should be "no".
Androgynous tops will generally be non-formfitting so that it doesn't define your gender. Specifically aiming to keep the chest area undefined.
-Loosely fit, flouncy tops and t-shirts
-Button downs, flannel
-Loose tank tops
-Androgynous pants are commonly straight-legged, but lately flare is coming back in style
-You don't want your pants to be too baggy because that seems very masculine
-Harem pants, or drop-crotch pants
-Boots are a very commonly worn in androgynous fashion, boots with heels are fine for both sexes
-Converse are common
-No 'girly' heels
-Sandals are fine
-Backpacks, messenger bags, no purses
-Unisex hats, like a beanie
-Any kind of jewelry is fine as long as you address the two questions above
-Neutral and earthy colors (browns and tans)
-Achromatic shades (black, white, grey)
-Commonly unisex colors like red, blue, and green (mostly darker shades)
-Neutral patterns, or no patterns at all
These rules are not set in stone, all fashion can be modified to fit your personal gender, fashion and gender are constantly changing, this is just one opinion by observation.