9/10 just adding eyelashes will make anything seem feminine. (It's the reason I thought Nermal from Garfield was a female for many, many years)
I'd agree with the comments about the glass-hour body shape, lips, but also... a bust is usually a good indication

The rest I think, is all about clothing. Although you could add false nails as well, painted. That's another one that suggests femininity (ininity?)