What are you
looking for in a good voice?
It fits the purpose or matches the character. If it sounds good, it's good.
you prefer to record/edit a voice
If it's recorded well with a good microphone then all you need to do is to crop the lines (so that you remove extra noises prior and after the voice take) and place the takes depending on how they need to be aligned in the project. You can also record in-place, so that the takes are aligned correctly or almost correctly already during recording. Process (this means compression and EQ) the voice, if it's needed to fit the purpose.
How do you interact with the
voice actor in order to set the right
tone in the recording?
Kindly ask for or discuss about a different kind of expression, if you think the actor could try something differently. Professional and/or experienced voice actors usually know what they do and can do. Remember not to be bossy, they're the artist, not you. Make the actors' studio and recording time comfortable. Just like singing, voicing is best performed when the artist is in a positive mood and feels comfortable.