Drink plenty of water to keep your voice hydrated and avoid coughing or clearing your throat when possible. Clearing your throat and coughing rubs the vocal cords together causing irritation.
Avoid drinking caffeine, dairy and alcohol to prevent excess mucous and drying out your vocal cords before speaking. All of these items will reduce the effectiveness of your voice.
Expand your vocal register by starting on a vowel in the middle of your range and then slowly bending the pitch downwards. Go as low as possible, but stop before you feel any pain. Try this exercise five times each day to gradually improve your vocal tone and range.
Practice speaking with a moderate rhythm. If you normally speak quickly, take time to slow down your speech and put pauses between sentences. If you speak very slowly, aim to make your speech more melodic and pay careful attention to the rises and falls at the end of a sentence. When you ask a question, your voice inflection should go up; when you state a fact or opinion, keep the pitch of the voice the same, or bring it down slightly at the end of the sentence.
Relax your tongue against the floor of your mouth when speaking. Ensure your jaw drops slightly and attempt to reduce any tension in your vocal cords when speaking. If you feel tension, relax the tension by physically allowing your tongue to lie flat and relaxed against the floor of your mouth. Practice saying words like "man" or "ban," that normally have a small degree of nasality in them. Soften the words by allowing the tongue to relax.