If there's a better place for this topic, please feel free to move it

I've been reading that the key to creating really great 3d objects or images is to make full use of both shading/shadows and highlights/reflected light. And the shading/shadows, I have a pretty good handle on. But I have a hard time looking at a 2d object or image, and imagining where highlights/reflected light should be.
Can someone recommend any instructional info on this, that I might read and study, and hopefully learn how to place highlights/reflected light effectively? I've done a fair bit of searching the internet, and haven't found anything of substance. Or is the age-old "practice, practice, practice" the only way to learn?