As the engineer, your key job is to select and set up the recording space, choose and position the microphone, set levels and make sure you're recording a good, clean signal at a healthy level. Like music, the louder the signal you want to record, the less audible the noise floor, but you don't want to have to speak louder than sounds natural, and you don't want to overcook things when tracking: any distortion will be very noticeable on an exposed voice part, and an otherwise great take with digital clipping won't be acceptable. If you notice clipping only when you start editing, software clip restoration tools might help to make the take usable, but it's not going to be perfect. Remember that although you may have needed to record 'hot' on analogue tape and older 16‑bit digital recording systems, modern 24‑bit A‑D converters can accommodate a much wider dynamic range, so you no longer have to track so loud: you can leave much more headroom.
Initially you will of course be a novice and even if you have a great voice, you will need to get yourself grounded in the industry. Again, this process will be down to how many hours you put in. Each person’s voice is individual and unique. For some people that means that they have a natural signature voice which is suited to certain types of voice over work. Other voice over actors have a natural passion for a particular aspect of the industry, such as character acting and so pursue their goals in that genre.

I use the Adobe Audition package to edit my own voiceover work, but the techniques described below can be used in most audio‑editing software. Start by saving a new version of your original recording. (I keep the name of the file the same, but change the extension from _original to _edit.) Next, I'll turn my attention to the end of the recording, where I stepped away from the mic after the second take and recorded about 10 seconds of silence. Although processing is usually kept to a minimum, dealing with sibilance is important, and Eiosis' De‑esser plug‑in is much more precise than most.Wearing headphones, I can zoom in on this 'silence', turn up the volume, and listen for any background noise. If I notice any constant noise seeping into the recording, I may consider using Adobe Audition's noise‑reduction tool to capture a one‑ or two‑second profile of the silence, and then reduce the offending noise by about 75 percent throughout the recording. I should stress that this is rarely needed, and it's always a last resort, because such processing can generate swirly, metallic artifacts that draw more attention to themselves than the noise you intended to eliminate! But it's good to listen for such issues with fresh ears at the start of your editing session. If you find yourself using noise‑reduction often, that's a sign that you should find a better place to record, or improve the isolation of the space you've chosen. Don't forget that there are other ways to deal with some noise: often, a high‑pass filter is all you will need to clean up a recording, for example. Also remember that if your recording is to be mixed with music, slight background noise won't be noticeable, and that the more exposed your voice in the end product, the more problematic noise will become.

Finally, as you complete more work, you can end up with a lot of different files from your projects, so good 'housekeeping' of your sessions and recordings is a must. Glancing at the filename simone_kliass_avast_virus_database_neumann_tlm_103_original.wav, I can easily tell that this is the original recording of my wife's "Your virus database has been updated” message in Portuguese for Avast! on a Neumann TLM103 mic. It doesn't matter what your system is, as long as it works and you can stick to it.
You start off each job as a producer, consulting your client and getting briefed on the project at hand. Then you become an engineer, dealing with recording gear and software, setting the mic position and levels. Next, you step up to the mic as an actor, bringing the script off the page and connecting with the listener. Meanwhile, the director in you sits behind the metaphorical glass, making sure the actor doesn't mispronounce a word or stumble through a passage of text. Then you're an editor, cleaning up the best take and sending the resulting audio to your client. You need to be able to perform all of these roles to a high standard, and the better you are at each, the more your business will prosper.
Before you get down to the nitty-gritty, though, I recommend doing a test recording to ensure your equipment works properly and your audio levels are strong. You don’t need to record the entire script, but a few paragraphs will give you enough to ensure that the audio is clear, at an appropriate level, and doesn’t include any stray or ambient noises.
If a client likes your demo, they may invite you to audition. In the 21st century, you can download the audition script, record the audition at home, and then send the results to your client over the Internet. Prepare yourself for a life of constant auditions: Even successful voice pros may do many more auditions than actual jobs. But if enough jobs come your way, it's worth it.
As editor, you need to turn the raw recording into the final version of the file you'll be sending to your client. Editing during a recording session can be problematic, and particularly so if you're recording in a domestic environment. How can you expect to hear the drone of the dishwasher ruining your recording if the dishwasher is still running as you edit? I'll look in more detail at setting up a voiceover recording studio next time, but for now, if recording in a separate room or isolated booth isn't an option, at least try to edit the file the following morning (or maybe at night) when there's less noise around — because hearing your recording with a fresh ear and in a quieter environment will help you to make better editing decisions, and will reveal noises that slipped your attention earlier.