There are several habits you can develop that will help you take care of your voice for voice acting.
The first, and most important, not only to your voice, but your entire body, is to drink six to eight 8-ounce glasses of water a day. Most people don’t do this, and it’s a big mistake. When you’re delivering a script, whether for practice or a final read, it is vital to keep your vocal cords in top condition. Keep the water at room temperature. Do not use ice. This is absolutely the single best approach in keeping your throat healthy.
Don’t go to sports events and shout for the team of your choice. This is very hard on your voice, and you could end up having to rest it for a couple of weeks to get your voice back to normal, if you want to learn how to keep vocal cords healthy.
If you feel dryness or are affected by post-nasal drip from allergies and the like, warm up a cup of water and add some salt to taste. Then gargle the full cup of saltwater slowly until used up.
If you have a lot of post-nasal drip on a more or less regular basis, I recommend a product called NeilMed Sinus Rinse. It comes with 50 or 100 packets that you dissolve in distilled water (bought separately). Fill an 8+ounce glass with the distilled water and eat it up in the microwave to a comfortable warmth (about 39-40 seconds). Remove the glass from the microwave and dissolve the NeilMed packet in the water. Add three drops of Johnson’s Baby Shampoo. This helps the water solution to adhere to the sinus walls to ensure a more thorough cleansing. Pour the solution into the squeeze bottle that comes with the NeilMed kit. If the water is a bit too warm, hold the squeeze bottle under the cold water spigot until it is at a comfortable temperature. Then stand upright and squeeze the bottle into one nostril and depress the other nostril to plug it. This assures that the solution will go into the upper sinuses. After each squeeze, let the solution drain out of your nose and mouth into the wash basin. Do the next squeeze into the other nostril. Continue doing this in each nostril until the solution is gone.
This is good maintenance for your sinuses and throat, and it is very gentle, in taking care of your voice.
Most ENT doctors don’t recommend any solutions for the sinus and throat that go beyond saline, except in extreme cases, where there is an infection.
Water is still the best preventive. Hydrate yourself every day. You won’t regret it. This voice over coach highly recommends it.