Keep your whole body in good general condition. Speaking is a physical activity and a healthy body creates a healthy voice. Get plenty of sleep, and exercise. Make healthy food choices and remember emotional attitudes directly affect the way you sound.
Reduce the stress in your life. Breathing is the key to self-healing.
If you become hoarse, immediately and drastically reduce your talking time. Save your voice for when it is necessary to speak. The same holds true if you’re sick, have a cold, allergies or any other affliction of the upper respiratory tract. Knowing how to use your breath correctly is a life saver during these difficult times.
Dairy products, milk, yogurt, cheese, and ice cream all produce excess mucous and should be eaten in moderation. Before giving a big presentation, I would avoid them. The same holds true for products with excessive yeast in them, beer, etc. are mucous producing.
Red Wine can have an adverse effect on sinus tissue. Rose and white wines are better.
Cigarettes need to be avoided. They impair your breath control and can cause cancer of the throat, lips, etc.
Keep your body hydrated. Drink plenty of fluids throughout the day: water, caffeine free teas and sodas.
Steam or dry sauna is relaxing to your body and voice after a long day of speaking. Using a bowl of steaming water with eucalyptus oil and putting your head over it and covering your head with a towel and inhaling deeply is a very cleansing.
You can also explore cleaning your sinuses with a nasal douche which uses a pharmaceutical saline preparation. This keeps the mucous from building up on your vocal chords.
Using a humidifier and air purifiers in excessively dry climates can keep your vocal chords and sinuses from drying out.
Keep your throat moist. Use cough drops. Avoid clearing your throat continually which can put excess stress on the vocal chords.
Ventilate your sleeping room with some fresh air.
Air conditioning and heating systems and plane air often can be filled with fungus and bacteria that affect your sinuses and lungs causing allergic reactions and breathing problems and therefore voice problems.
When one is exposed for a long time to mold, it can cause upper respiratory conditions, such as bronchitis, asthma, chronic sinus issues, all of which affect the quality of your speaking voice.