Most people you will meet will be water dry- or dehydrated skin. Even if you're oily- you can be water dry. Your body is lacking water therefore your skin is lifeless, dehydrated, and can even overcompensate for the lack of water by producing more oil- causing you to break out.
The best way to help water dry skin is to replenish that water loss. Your best friend will be water. I've been experiencing this lately (moving to the desert doesn't exactly do wonders for your skin), and I've been using an awesome toner and water based moisturizer to lock in that hydration. Drink plenty of H2O and make sure you're eating foods packed with water. Then of course there's sunscreen. The sun is super drying on your skin, again, causing it to over produce oil to make up for the dryness. Protect yourself! Wear that sunscreen!
Then there are those people that are oil dry. You'll know them by their small pores and flaky skin (not saying they'll all be shedding, but you know what I mean). Because of your lack of oil your skin is missing that natural hydration it needs to stay young and healthy. If not taken care of properly, dry skin tends to age quicker than oily skin. And just because you don't produce as much oil, doesn't mean you won't have acne. On the contrary- you'll have dry acne. You need to stay so hydrated with an oil based or a more heavy moisturizer to give your skin that drink that it needs. When choosing a makeup, go for a more cream foundation that's going to keep you hydrated and a mineral powder to set it in place.
My best tip for those with dry skin- MOISTURIZE MOISTURIZE MOISTURIZE
Here's what my daily routine would consist of if I had dry skin:
exfoliate (2-3x/week) to break up those impactions and slough off the dead skin
moisturizing masque (1-2x/week to really hydrate that skin)
eye cream (did you know most women should be wearing an eye cream starting at age 19?)
moisturize with a heavier or oil based moisturizer (apply while skin is still wet from the toner to lock it in)
cream foundation (one that's non-comedogenic- won't clog your pores)
All of that moisturizing talk may have you worried that you're going to break out. Remember- your skin is either A) over producing oil because of the lack of water or B) not producing enough oil to keep your skin hydrated. BOTH of those things can cause you to break out. You need to moisturize to balance your skin out. Trust me. Your skin will thank you. :)