When we think about dry mouth what comes to mind first is the lack of water intake so the obvious choice must be to get enough water systematically over a certain period before having an extensive search for any other remedy or supplement without covering the basics. If the dry mouth isn’t severe people can try supplements for dry mouth such as herbs that can enhance the production of saliva such as marshmallow root, ginger, pilates, nopal cactus, sweet pepper, hollyhock root, and others.
Breathing through your mouth is a habit that can worsen dry mouth. To battle this condition it is often enough to exclude a number of medications and substances from your daily diet some of which are hormone medications, antihypertensives, antihistamines, bronchodilators, caffeine, alcohol,tobacco, and sugar. However, if the problem is persistent and is starting to get serious than its preferable to visit a physician to determine the cause and accordingly provide you with the treatment applied to your particular situation. 
That would be in all probability to prescribe medications that enhance the production of saliva, prevent your teeth from having cavity trouble, the mentioned switch from medications that may be the cause for dryness or to try out products meant for moisturizing your mouth mostly being mouthwashes containing xylitol.
Good communication with your doctor can prove to be the determining factor so be prepared to give quality answers that will provide you with a better chance to be diagnosed properly. Be sure to be able to name all the medications and supplements for dry mouth that you are currently taking along with the dosages, seemingly unrelated current and past conditions can prove to be of significance,information about your life, in general, is also an credible source of information and should not be left out. Be ready to answer the common questions about the period during which you are experiencing the mentioned problem and how often.