Depends...my favorite ways to use it are to set my makeup (spray lightly over your face when your makeup is done), to dampen my brush when I'm using a shadow as a liner, or applying pigments, and best of all (for me, anyway) as a skin refresher. I pop it into the fridge during the summer, and after I've been outside and I'm feeling gross, I blot my face off with a paper towel, and spritz it all over my face and neck. It feels like heaven, and keeps your skin moisturized.
i use it for a skin refresher, sometimes a finish spray for my face make-up, a spray onto the brushes to make a certain face product glow, and also as a mixing medium for shadows/pigments!