Hi Nova SS,
In addition to staying very well hydrated, here's a number of other steps you may wish to consider:
1. Purchase a reg with "moisturizing fins" in the second stage, such as the Oasis & Blizzard made by Sherwood
http://www.sherwoodscuba.com/regulators.html .
2. Purchase the Apollo reg which has a "moisturizing chamber" into which you place a small, damp sponge; or get one of Apollo's in-line Bio-Filter mositurizers
http://www.apollosportsusa.com/Products/Regulators/index.htm. IMHO, this probably is not worth the considerable expense and is another failure point in the gas delivery system.
3. Purchase a "Scuda" or "Camel-back," nifty little diver's canteens which allow you a squirt of fresh water when you want it
http://www.scuda.com .
4. Tickle the roof of your mouth with your tongue, or run it along your teeth, as this will trigger salivation.
5. Rub a very small bit of toothpaste onto your mouthpiece prior to entry.
6. Contact Laclede's (800-922-5856) for free sample packs of their artificial saliva products, which I hear are quite good.
What you do not wish to do is enter the water with anything in your mouth that could be aspirated, e.g., hard candies.
Best regards,
DocVikingo