Does anyone have a way to stop breathing thru the mouth during sleep?

I had no idea I was breathing thru my mouth instead of my nose until recently as I started getting a very bad dry mouth several times a night and would have to take a sip of water to clear it up. I checked on the computer as to why and found it was because of breathing thru my mouth. I then began to ask how to stop, but so far, I haven't been successful, but since I am now aware of it, I am trying my best to stop. I also have had dry, cracked lips for years and my Dr. had no answer. However, I have found it has to be because of breathing thru the mouth, as I have had a little success and noticed the lips are beinning to get better. Has anyone had this problem and have found a solution? I am going to try taping my mouth shut when I go to bed. I read that may be a solution, too. I hope I can break myself of this.