Voice Overs

I am a noob, but Im curious as to how you guys (animators/directors/producers) handle the voice over portion. What I mean is, where do you find your actors, and being that in animation, its not voice over but its voice guides meaning that the voice is the backbone of the animation which provides the initial feel of what type of animation you will be doing, like first getting the script, having the actors say their lines and then animate in 3D world.

Find them wherever you can, or post your script and see if someone would like to do it. If not having the voice / sound files is stopping work on the animation you can always make placeholders by recording yourself before finding a suitable actor.