First, I like to listen to the entire voice over recording from start to finish. I may make notes here and there to remind myself of something I want to go back and edit, but this time through I really just want to concentrate on the overall pacing and tone of the recording. Does it sound like I hoped? Did I rush or speak too slowly? Did I flub any words, mumble, or misspeak? Are there weird silences or unknown sounds?
Be mindful of the sounds of your heating and cooling system (this goes for a home recording studio, as well). If you can’t find a spot where you can’t hear air rushing through your ducts, you may want to shut down your furnace or AC for the duration of your recording. If your recording space is near a window, listen for sounds of traffic — especially loud trucks. They will definitely show up in your recording.
Your own voice is your most important piece of equipment. If you're new to the voice-acting world, look around to see if there are classes or coaching in your area. Outside of class, practice speaking clearly and confidently. Learn to do this even with material you've never seen before. It's also important to learn voice care – straining or injuring your voice can hurt you and your career.
When asked by someone outside of the industry how much I’m compensated for a commercial voice-over, I can see their eyes grow large with excitement. It may sound like a large number for two or three hours of studio time, but what is not understood is the investment in time, money and education that it takes to begin and sustain a voice acting career. As voice-over professionals, we need to remember (especially if we are setting our own rates) that the time we have spent in classes, coaching sessions, and our booth add up to our expertise in this field. When setting your own voice-over rates, or negotiating those set by producers and/or clients, you need to not only consider your session fee (the time spent in the booth recording the specific copy), but also all the training you’ve acquired and the investment in your home studio (which helps make your client’s job much easier).