1. At night, cleanse your face twice. In a row. The first cleanse will wash away makeup and grime your face collects while you go along your way. The second cleans into the pores and preps the skin for treatment products to follow. I use Olay Foaming Face Wash for Sensitive Skin as my first cleanser (but I absolutely love Neutrogena's Ultra Gentle Daily Cleanser, too). I rinse well then immediately follow with SkinMedica's AHA/BHA Exfoliating Cleanser. Treatment products will absorb and work better.
2. Use sugar as a facial scrub (up to 3 times a per week, if your skin can tolerate it, but no more). Just add a few tablespoons to your favorite cleanser, gently rub onto skin, and rinse. Sweet! (You can also use salt.)
3. Day time products with retinol can increase skin sensitivity to the sun and should only be used at night. Vitamins C and E work great together and are a perfect pair for daytime use.
4. Apply treatment products to dry but still moist skin. They'll absorb better. Prescription products should only be applied to thoroughly dry skin, unless otherwise prescribed.
5. If you're using hyaluronic acid to increase skin's moisture, immediately follow with regular moisturizer. If you don't seal it in, it'll simply evaporate.