Clearly Communicating Your Vision
We've already discussed a few different aspects to consider when deciding on what sort of voice—and thus voice actor—would work best for a project. We've talked about tone, vocal “age,” and even accents. So let's say you're ready to put all of that together and either set up an audition or contact an agency like FlyVoiceovers to find the right talent. Here are some suggestions that can help ensure your vision is communicated clearly to the agents and talents both during the casting process and once the project is set to record. This way you get a more relevant pool of talent auditioning, and they know exactly how to deliver the read once they're cast.

Be as precise as you can when explaining the feel you are going for. Like we previously discussed, keeping things vague with something like “conversational” even if it's a script about corporate procedures can potentially lead to confusion. We have different conversational tones depending on the situation and our relation to who we're talking to. So really think about exactly what you are looking for and describe it as best as possible. Don't stress about using industry standard language, as the important thing is just to get your idea across. After all, those “industry standard” terms can, as we pointed out, be a bit vague. So saying, “Sound like you're discussing recent events with your neighbor on the porch while drinking coffee in the morning,” can be considerably more helpful than “friendly and conversational.” This is your project, your vision, and the talent wants to do what they can to get it done right. Being as descriptive as possible in what you're looking for will help them immensely!
Offering comparable voices is always an option, if you feel that would get your idea across more adequately. It's pretty common to see famous actors listed as comparison voices in auditions, and lets people know right off the bat if they have the kind of vocal tone and timbre you want. But make certain that if you list multiple names, they are in a similar vein. Do not, for example, list two actors from opposite ends of the pitch spectrum, or who have completely different accents, or sound like they are vastly different in age. This will only confuse the talent/agent, and make it difficult to determine exactly what you're looking for. Perhaps as a good way to help you determine which actors to use as comparisons, you could consider who would be your top choices based on our previous posts about tone, age, and accents. What is it you are looking for in a delivery, and what actors most accurately fit that? This should give you a list of actors with very similar voices, which in turn helps agents and talents have a cohesive idea about the kind of voice you're looking for.
Have a set concept of the length you want the delivery to fall within, so the talent will know how they need to pace themself. With this, though, also make sure that your script can be read at the pace needed. If you have a very wordy script that you need to have fit within a minute, it will be read at a very fast and likely unnatural pace. Try reading it while timing yourself. If you feel you are rushed to get it all said in time, so will your voice actor. See if there's anything that can be rephrased so that it uses less words, streamlining it, so that it can have a natural and likely more engaging read. We offered tips on script crafting in our last post. If there's no time limit, and you want your voice actor to speak at a leisurely pace, communicate that. Pacing helps to set the tone and feel of things, and therefore is just as important as any other aspect.
You're probably noticing by now that communication is the key, and it really is. First and foremost you should know exactly what you need, so that you'll know exactly what to communicate. Don't ever feel afraid of communicating too much, as the more details that are given, the less likely there will be a need to redo anything. But don't let this make you feel like you have to have a very strict concept with no flexibility. It is perfectly fine to have a range of concepts you're looking for or want the chosen talent to fall within, so long as you still try to communicate that as clearly as possible. For instance, you may be fine with any age from 25 to 60. Just be aware that if you are holding auditions, the more ranges you list, the more varied your responses will be or the more difficult it may prove for an agent to narrow down what you want.
Think of it like online shopping, and the more filters you put in, the more refined the search becomes. Being specific will narrow things down until you finally find that perfect voice your project.