People ask me how I come up with the different voices for my puppets. Here are some thoughts:
Let the face of the puppet remind you of someone and talk like they do: Just today, I was playing with this little raccoon, thinking of how it should talk. It had a frizz of hair below its chin which looked like a goatee, a mouth with a wry twist and black “burglar” patches that looked like dark sunglasses. Suddenly I had an image of a beatnik. I opened my mouth and this hip, with-it kind of voice came out (but pitched a little higher, since this is a cute little furry thing).
Try different voices until you find one which clicks: Willy the Wolf is the star of most of my puppet stories (have a look at some of the stories on http://www.wondroustales.com/video.htm). I have a warm furry, gently silly voice for him. But when I started using that puppet, gosh, 25 years ago (!), I gave him a stately, intimidating British voice and made him the wizard hidden at the end of the underground maze. But that just never worked for me, so I kept trying.
Shape your face and mouth like the puppet's: Purse your lips in just that way, arch your eyes, put on that silly or wise or snarky expression. What emotions do you feel? What do you want to say? Open your mouth and let it come out.
Feel your hand as the soul of the puppet and let it talk to you: So if there was a little person there at the end of your arm, how would it talk to you?
Still stuck? Just play. Talk in a high pitch, then a rumbly low one. Talk bubbly fast, then syrupy slow. Stick your tongue out and make a silly face! Maybe have the puppet start to tell you about itself.
Have fun. Share with me any ideas you have and let me know if this was useful!