Here's a video I made a few years ago but still is just as valid today, and many people have said this 15 minute ad-lib has been most useful to them when starting voice acting to win auditions; one message saying they learnt more from this video than from a year in drama school! See what you think; it contains some personal thoughts, some acting theory and then a drama exercise for you! Please post if you have further tips or if you disagree with me!