Here some tips on using your voice from City Academy, here:

1. Always warm-up. Do this before every audition, every rehearsal and every performance. Even five minutes makes a big difference, so try to fit in some mindful voice work every day.
2. Practise sight reading. This is when you recite books or scripts you’ve never read before, out loud. It’s an essential part of almost any audition and the more you do, the better you get – remember to look up at the end of thoughts, this will help you be more convincing.
3. Breathe at punctuation. It may sound obvious but punctuation divides text into thoughts, helping you make sense of it. So it’s important to breathe at punctuation to gain a better understanding of the character’s thoughts. Be careful though, if you breathe when there is no punctuation, you will be in danger of unintentionally transforming that speech into a list.
4. Relax the jaw. This is so important, as it creates room in the mouth for the tongue to move freely, which is the part of our mouth that actually creates the shapes for us to articulate sounds, so it really helps with oral resonance. Try saying “ahhhh” with a tense jaw and then hear the difference when you allow the jaw to drop open.
5. Strengthen your tongue. Do exercises such as letting the jaw drop open and pointing out the tongue, touching it to the top lip, bottom lip, top teeth, bottom teeth, top gum ridge behind your top teeth, and the bottom gum ridge behind your bottom teeth, the hard palate and the floor of mouth. Repeat the sequence five times and don’t forget to breathe or make sure that the jaw remains relaxed!
6. Shape the words. Each word has a different combination of vowels and consonants that give it a different feel when spoken. Try to become more aware of the physical sensation of speaking these, particularly when practising sight reading.
7. Practise good alignment. Your body is the carry case for your voice, so if your posture is aligned correctly, your instrument remains in good condition. Imagine your pelvis as the foundation stone of the spine, and try to be tall through the back, so that your neck is straight, rather than curved.
8. Yawn. This is an easy one for most of us. Yawning is one of the best voice exercises you can ever do, as it lessens constriction in the throat. Indulge as often as possible and always make it part of your warm-up.
9. Breathe consciously. Breath is the power behind your voice, but it’s so easy to allow it to become restricted – once in a while we all forget to inhale, perhaps if we’re stressed or shocked. That can lead to shallow, throaty vocal delivery, so try to let the breath drop in deeper and as you breathe out, sense how the stomach muscles contract to help the diaphragm push the air out of the body.
10. Drink water. One of the most easily forgotten points of vocal health is making sure you are well hydrated. Drink at least a couple of litres a day and carry a bottle of water around with you, so you make a real splash while doing any type of voice work.

Here are some more tips, from Samuel L. Jackson:

1. Commit to doing vocal warm ups. An important part of preparing for a voiceover job or voiceover audition is warming up your voice through voice exercises. As Sam explains, most actors are familiar with vocal warm ups from theatrical work. Vocal warm ups and breathing exercises are a useful tool to prepare for any sort of performance, but they are especially useful when preparing to do voiceover work. Your own voice is the only performance tool available to you in your voiceover career. Warming up your voice and practicing enunciation can help you ease into a “recording voice” that has the appropriate breath support and clarity for audio recording.
2. Do research when creating characters. Part of creating distinctive characters with specific vocal patterns is doing all the normal research and exploration you would do for a live action film or theatrical production. Once you have a good sense of who your character is, you can practice speaking your lines and feeling out how you might approach the dialogue. It’s important to work with the text extensively before it comes time to record. Practice is a huge part of creating distinctive, memorable characters. For Sam, recording audiobooks have given him practice at creating multiple characters and alternating between them.
3. Find vocal tics. One way to differentiate characters as a voice artist is to find specific vocal tics. Having a good voice and proper enunciation is a great start towards becoming a voiceover artist, but professional voice actors must also find ways to incorporate the nuanced ways that humans communicate. Sometimes this involves specific vocal tics or impediments.
4. Play with energy. A lot of voiceover jobs involve recording material for video games or animated films geared towards a younger audience. Sam says that learning to vary and channel your energy into your work can help produce engaging voice performances for younger audiences.
5. Overcome your speech impediments. Sam is known by many for his booming and commanding voice, but this wasn’t always the case. From a young age, Sam suffered from a stutter, but he overcame his speech impediment through practice. There are many professional voiceover actors who have minor speech irregularities that they have overcome. The good news is that through practice, voice and breathing exercises, and professional speech therapy, most speech impediments are treatable and should not prevent you from becoming a successful professional voiceover artist.
6. Find a universal voice. Sometimes as a voiceover actor you will be asked to perform as a real life, recognizable character. While learning the intonations and speech patterns of your characters can be useful, Sam explains that he favors an approach that is deeper than just superficial mimicry. Rather than doing an imitation of a real-life character, he tries to forge a deeper connection with their words and find a voice that feels appropriate and accessible to audiences.
7. Practice. It’s important to practice even when you aren’t in a professional recording studio. Many professional voiceover actors have home studios for recording voiceover acting auditions and honing their voiceover recording skills. It’s easy to set up a home studio, and the only equipment required is a microphone, headphones, and a computer with recording software. Once you have a full setup, practice reading copy and listening back to your recordings. This will help you in your voiceover training as you develop a professional-sounding voice that will appeal to casting directors and audiences. If you’re using your home studio to self tape auditions instead of auditioning at a professional studio, make sure that your equipment is producing professional-sounding audio and that there isn’t any noticeable background noise.

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