I am hardly a makeup expert, but as I understand it, you can imagine a light shining down from above. The highlights will be lighter, such as the nose, cheekbones, forehead, and chin. Areas in shadow get a darker shade, such as the neck, below the cheekbones, under the chin, sides of the nose, etc. You would blend between the two so you don't have lines of contrasting color. Lighter under the eyes and in the inner corner, makes them stand out. Darker under the brow (eye shadow). You will need to practice and try different shades to figure out what works for your bone structure. The other advice I was given is when applying coverup or foundation using your finger to apply will give a lighter layer and a more natural look. Using a sponge will give you better coverage, but can start to look caked on. I have larger pores so I use liquid. Powders like Bare Minerals tend to settle into the pores and make them stand out.
Hopefully, you will find something here that is helpful.
Hugs!