How to Throw Your Voice. Ventriloquism depends on the ability to throw your voice--to make the dummy appear to be speaking while you seem to remain silent. It's a subtle and very difficult skill, often taking months or years to learn, but you can do it if you apply yourself and follow some reliable steps.
Learn to breathe through your nostrils. The mouth is the instrument by which you will throw your voice, and trying to breathe through it while you work is like trying to juggle and wash dishes at the same time. It sounds obvious, but it takes awareness and practice to breathe through your nose consistently.
Take in a deep breath and hold it for as long as you can. Exhale, and repeat. Deep and sustained breathing is vital to learning how to throw your voice, since you may have to talk for up to 90 seconds between breaths. Work on holding your breath for as long as you can for a set period each day, making it a routine and practicing it until your lung capacity increases.
Practice making a sound akin to a bee drone. Place your tongue flat against your mouth and push the sound upward from your abdomen through your larynx towards the roof of your mouth. This technique produces an effect similar to a sounding board. If performed correctly, it can fool listeners into believing that the sound comes from a height or a distance. This is known as the "sky technique."
Repeat the process without trying to force the sound to the top of your mouth. Instead, curl your tongue against the back of your teeth. This effect (the "level technique") can make your voice sound level to you, though still at a distance to others.
Repeat the process again with your chin thrust forward and your larynx contracted as much as possible. This appears to move the bee drone sound to a lower physical level, near the floor. It's called the "ground technique."
Practice switching between the 3 techniques until you can move back and forth between them with ease.
Modify the "bee drone" sound with other sounds, working on them until you have mastered emitting them with your tongue in the 3 positions described. The more you practice, the more readily you should be able to compose specific sounds and words using only your tongue to modulate their location.
Switch between techniques to enhance the illusion that you are throwing your voice. For example, speak to your audience using the "level" technique, then appear to emit a second voice from above their heads using the "sky" technique. The shift in tonality will produce an aural illusion, whereby the second voice will appear to come from above their heads.
Visit the Ventriloquism in a Month website for more techniques and tips (see Resources below).
Traditional vocal control, such as learning to sing or speak in public, is very helpful when learning to throw your voice. Consider studying these alternate methods as a means of helping to develop your technique.