So you got your BFA, MFA, maybe even PHD in acting? Your voice sounds like Morgan Freeman after eating raw honey? Amazing! But that may not mean you're ready to jump in and be a pro at voiceovers. There are great commercial and promo voiceover artists who have never acted before in their lives, and there are plenty of people with beautiful voices who can't cold read for the life of them. You'll definitely have a huge leg up if you have an acting background (especially in animation and video games, which are most like stage and film acting), but voiceover is a whole different animal. I found this out after going to eight years of acting school, and after having auditioned for voiceovers since I was seven years old. Even to some successful on camera actors, voiceover is still a mystery (and a lot of it still is to me). I get emailed a lot for my advice on how to break into voiceover, so I made this page to share with you! This is more geared towards the VO newbie, so I apologize if some of this doesn't apply to you.
My first and most important bit of advice is to take classes. What kind of classes you take depends on what area of VO you're interested in (or if you're into all of them that's great too). There's commercial voiceover, animation/video games, and promo/affiliate (promo is "tonight on Scandal" type thing, affiliate is when you're the voice of a local news channel and its a contractual weekly gig usually). The last two are harder to get through an agent, so it's good to self submit and send your demo when you have one to local networks (for affiliate). Promo/trailer work usually come via a manager, so submitting yourself to managers once you're working a certain amount/have credits is helpful in that area.
VAN is a great way to get started, it's where you can do workshops to meet casting directors, directors, and agents.
2. Richard Horvitz http://www.richardhorvitz.com/classes-a-coaching/classes
Richard is great if you're into animation (or commercial), he comes at it from an actor's POV and helps you really find the life in a character (and also is good with commercial copy). He's good for when you're starting out but also just good as a workout class.
3. Lori Alan http://www.lorialan.com/coaching
Lori coached my animation demo (produced by Susan Palyo at Voicetrax West) and is really great if you want to focus on honing your animation voiceover skills and do private coaching and audition specific coaching.
Jodi Gottlieb teaches Promo classes, so if you're into that she's the best!
Carroll Kimble is one of the only few actual VO casting directors left and she teaches classes (contact her through her casting email). I would recommend this if you're really focused on doing commercials. Another good casting director who teaches classes is Elaine Craig http://www.elainecraig.com/voice-over-workshops-and-events/, as well as Kalmenson and Kalmenson http://www.kalmenson.com/class-schedule.html
6. If you really want to focus on commercial work and are serious about it as a career, I recommend Nancy Wolfson http://www.braintracksaudio.com/ She does private coaching and has a whole curriculum that breaks down commercial voiceover almost mathematically. Then at the end of it she can produce your commercial Demo (which can costs a lot, but is worth it).
In terms of a demo: paying for a good demo producer is worth it. I would say don't make a demo until you've trained a little bit, and the teachers you meet will guide you in that way. Richard Horvitz produces animation demos, and I'd recommend Nancy Wolfson for commercial. You basically just need an animation demo and a commercial demo (both about 1 min to 1:30) initially, if you're interested in both areas. But I would still wait to do those, you don't want to make it before you've honed your skills, otherwise its a waste of money. Then when you have a demo, you can submit your demo to agencies by mailing them an MP3 of it. Susan Palyo at http://www.voicetraxwest.com/ is a great demo producer, and Voice Trax is also a great place to look at for classes.
In terms of auditioning, when you're just starting out and are non-union, https://voice123.com/ and https://www.voices.com/. have a lot of available jobs, but don't pay very much. It's very worth it to try to get into SAG/AFTRA once you have a demo. Non-union work may seem like a good amount of money at the time, but most of the time if that job was Union, it would have been much more money. You're worth it! Also, if you end up doing Nancy Wolfson's class, she may start sending you auditions through the agency she partners with.
Cold submit and use your friends with voiceover agents as referrals. Send postcards and MP3's, make 'em notice you. There are also a lot of great Voice Over agencies all over the US. Even if you live in LA or New York, you can submit and sign with regional agents in Texas or Illinois to broaden your audition pool.
So my advice is:
1. Take Classes
2. Create a demo/audition for non-union projects on voices and voice123 (if you're non-union)
3. Submit yourself to agencies (either through a referral, or by cold sending your demo via MP3 or even *gasp* a CD in the mail).
In terms of microphones and ways to audition, these are some of my favorite cheap mics to use on the go. You should also eventually invest in a great home mic, which you can test and purchase at any Guitar Center. But guys, technology is amazing and you can record and book from your phone now!
So there you have it! I'll probably keep adding to this so check back!