Plug your nose with your fingers. Breathe into your stomach not your chest and say something. If you have a funny voice you should speak lower until you don't. Chances are you were taught to speak with your nose. For example, if you try to talk with a Mexican accent you'll notice that you're going to be using your nose a bit more than usual if you pay close attention. Same thing when you try to speak with a stereotypical Russian accent(like that Georgian character from GTA IV). Don't hurt your throat and remember that you don't have to sound like Barry White.