get familiar with the 2 bits of anatomy...
if there is a white hair -- Female bit, always. as far as preflowers (develop in nook of a limb before flower development), there will only be 1 nub. (symmetrical growth early on will have 2 preflowers per growth node, but split apart on each side.)
male bits will look the same initially, but they will never pop a white hair. they will also form a twig-like projection from main stem.. then, more will grow in that same cluster, unlike a single calyx mentioned above.
there is plenty of time to let this stuff grow out for easy identification. no worries about accidental pollination if you keep an eye on it. the pollen sacs must open up and a bunch of 'nanners' will be exposed... you can see the color change from green before this happens. if you find lone 'nanners' without a sac in your buds, this is less of a problem. you can pluck individual nanners and have very few seeds. (they aren't producing much pollen and none at all while green and maturing... yellow is mature but they don't produce much pollen typically. 1 sac maturing and opening will pollinate entire room, on the other hand.