Starting by looking at your wrists if you look at the colors of the veins you can start to see what kind of undertones you have. If you have blue veins then it would be more cool, green veins would be warmer, and if you see both then you are more likely to be neutral. The next way to check is by holding a white piece of paper up to your skin so you can see in a mirror based on what color the paper looks like, is it reflecting? One of the final tips is whether you look better wearing gold or if you look better wearing silver. This will help you determine what colors will work best for you when you wear makeup.