>>3718409Low-key photography is characterised by areas of contrasting lighting. While high-key photography uses even levels of lighting.
The best thing you can do if you're learning lighting set-ups is to get a good light meter of some sort (if you're really strapped for cash use a light meter phone app), set its shutter speed and iso to remain static then spot measure the lighting set up on your subject using the aperture it comes up with as a reference for how light/dark something is and what ratio of how light/dark you want your lighting set-up to be. So using this system, if I were to do high-key lighting and wanted everything even I would want my Key light and fill light to be on a 1:1 ratio and the light on my subject's face would measure f11/f11 on both sides, using powerful lights. If I were to be doing a low-key lighting set-up, I'd want my subject's face to be, for the sake of an example/ f11 key light, f5 fill light. Play around with different ratios like this with a light meter and different set-ups and you'll learn a lot.
Also if you want to do it "properly", keep in mind photography is a creative art, so to answer that question you want to take a step back from your photo and ask "What am I trying to accomplish with this photo?" Once you can answer that question you'll be good.