Drinking plenty of water is probably the easiest and first step to help a dry mouth.
Medication can also cause dry mouth. Check on any medications you take regularly and see if the side effects of any of them cause dry mouth. For example: Claritin-D has a decongestant and can cause a dry mouth.
Also here's some stuff I got from
WebMD
steps you can take that may help improve saliva flow and protect your teeth include:
-Sucking on sugar-free candy or chewing sugar-free gum
-Drinking plenty of water to help keep your mouth moist
-Protecting your teeth by brushing with a fluoride toothpaste, using a fluoride rinse, and visiting your dentist regularly
-Breathing through your nose, not your mouth, as much as possible
-Using a room vaporizer to add moisture to the bedroom air