Picture via Elle.com
If you have a round face like Drew Barrymore, your best option is to use long earrings that makes your face look a little bit longer. See the pictures how she is using long dangle earrings. Also try that they are slim. Another option would be large Hoop Earrings which will also make your cheeks look slimmer.
Picture via Fashionfame.com
If your face is more oval shaped avoid using long earrings, try instead filling out your face with shorter earrings. You can use Studs, Chandeliers or Chunky Earrings. An example of a celebrity with oval shaped face is Sarah Jessica Parker.
Photo via Filmfestivals.com
Women with heart shaped faces look the best with earrings that are small at the top and chunkier at the bottom, like Chandeliers or Hoops with something the bottom. What you need is to add some volume under your cheek bone. Reese Witherspoon is a good example of a heart shapaed face.
Hoop earrings are your best option if you have a square face, also round Studs and Chandelier Earrings. They round shapes will soften your face a little bit. See Demi Moore's picture, she is wearing large hoop earrings which match perfectly to her face.
Remember that your hair style and clothes will also make a difference, but I think this is a good start. Let me know if you have any questions and Have a Great Weekend!!!