But women don't perform femininity naturally. Especially not ones who aspire to be "ladylike." So much of femininity is a learned performance - how to stand, how to walk, what to do with your hands, how to speak, all are taught. Upper-class girls used to get sent to "finishing schools" to learn these very things. Now most girls learn from each other; they may behave in ways their mothers wouldn't deem entirely ladylike, but they aren't natural either - they're just learned in a different way.
It's true that these days, unless you're in your seventies or a British royal, you probably don't want to act like a "perfect lady." But you probably should try to match your mannerisms to your age, the way you dress, and the social class you want to portray. Sure, if you're wearing a tank top, fatigues, and combat boots, you could go ahead and have really masculine body language - cross your arms, lean against the bus stop with one foot up on the glass, spit and glare at passers by. Some girls do that. But the same body language in a nice blouse, designer jeans and heels...that'll get you stared at.
So if you're not sure what body language matches the kind of woman you are or want to be, it's worth asking, and then integrating whatever elements of it mesh with what comes naturally to you. Doing that isn't any more inauthentic than reading women's magazines or asking for makeup tips. (Can you imagine the catastrophe if women were just told to apply their makeup in whatever way came naturally to them?)
In answer to the original question, I never did quite figure out what I was supposed to be doing with my hands while standing still not carrying a bag. Carrying a bag greatly simplifies the question - I wouldn't do it, because purses symbolize womanhood to me, but obviously for you that's not a problem. An alternative if you carry a cellphone is to play with it. The main thing seems to be to try holding or playing with something, and not leaning on anything or sticking your hands in your pockets.