There is a huge amount of information and advice on line on how to be a voice over artist.
One of my favourite sources of information and entertainment for all things voice related are the various free training videos posted by voice coach Nancy Wolfson. I rediscovered one this week that I had first seen a couple of years ago.  Despite being a few years old I think the content is still relevant.

Nancy is coaching a male VO on stage at a VO conference and her focus is on getting the MVO, Loren Fry, to relax while reading a script for a TV commercial.  He’s got a great voice but his first read of the copy “sounds like a radio spot” according to Nancy. She argues that the role of the voice in a TV commercial is a narrative that supports the pictures, frames them rather than taking centre stage. You need “more hush on your voice and lengthen your vowel sounds” is part of Nancy’s direction.

She is a also a great believer in holding your copy up at eye level so you don’t lose your voice performance due to looking down at the words – and so becoming slightly off mic.
Nancy tries several strategies to get Loren to relax his voice – with varying degrees of success. However she is still not happy with the performance and so eventually (at around 4:52) she gets him to lie on the floor and do the read there.  It certainly makes for a more relaxed voice tone!

It’s not practical for a real VO session of course but Nancy argues that by practising reading while lying down you will feel what your body feels like when relaxed and so you can subsequently use muscle memory to access that feeling when doing a real voice over – even while standing up.

You can see the video here:

Chris Radley – Voice Over