The exfoliants found in face wash are the little scrubbers that wriggle dirt from your pores. When choosing an exfoliant: size and density matter. The skin on your face is thinner than the skin on your body, so using a large, coarse exfoliant like apricot shells can do more harm than good. You're looking for something that loosens dirt gently enough not to damage your skin, meaning you shouldn't be able to see and feel big, chunky bits when you squeeze a little onto your hand. Go for something finer and gentler like perlite (a cool volcanic rock that's full of moisture and puffed up more than 30x its original size to resemble something shaped like popcorn) to loosen dirt without damaging your moneymaker.
Surfactants are the "SURface - ACTive - agENTs" found in cleansers that reduce the surface tension between two liquids or a liquid and a solid. So whereas exfoliants act to loosen dirt from pores, surfactants are what lather up and lift the dirt away from the surface of your skin, trapping it until you rinse it off. Surfactants do pull away the dirt, but the wrong ones can be harsh and leave your face irritated, especially if you have sensitive skin. Be sure to avoid big offenders like SLS (sodium lauryl sulfate), or seek a face wash that’s “sulfate-free”.
Facial cleansers have a tough job: remove the dirt and as little else as possible. Unfortunately, it's impossible to find a face wash that actually cleans your face and doesn't remove at least some of the moisture from your skin. Fortunately, a good face wash has ingredients in it to counteract the drying effect of its cleansing agents like shea butter, aloe or panthenol (a compound found in ointments, shampoos and conditioners that pulls moisture from the atmosphere and pulls it into your skin to hydrate it). Avoid anything that gives you that "squeaky clean" feeling reminiscent of your acne-riddled teen years.