There are a few simple things you can do to maintain a good level of moisture in your skin for benefits such as:
1. Drink enough water - space this out through the day. If you guzzle down a litre just before bed because you've forgotten during the day then A, it'll mostly go straight through you and B, you'll have disrupted sleep because you need to go to the toilet.
2. Fill your meals with lots of fresh veggies, fruit and soups.
3. Ensure you have enough carbs and salt in your diet to help absorb the water that you get from drinking and eating.