Varying pitch. To avoid talking in a monotone raise and lower your voice to emphasize or de-emphasize certain points in what you are saying.
Soft volume. Speak just a little softer than you normally would, especially when talking to someone who is standing near you.
Relaxed tone. If there is tension in your throat or chest, your voice will sound hoarse and forced. If in a stressful situation, try to do breathe more deeply to relax the muscles in these areas.
Gaps: Speaking without pausing causes people to feel uncomfortable listening, and even tired. Pausing gives the speaker a sense of authority and the listeners confidence in what is being said.
Smile: When you speak, make your voice “smile”. Try to smile without actually smiling!
Have fun making your speech more friendly – see how people react differently when you speak!