Veteran actor Bob Fraser has a ton of acting career advice on his Show Biz blog. 40+ years worth.

I just recently found Bob's series of articles titled, " How To Get An Agent", Parts 1, 2 and 3.  While some of the material is geared toward on-camera work, many principles apply to the voice-over world.  After all, we are voice actors.

What I enjoy about these posts is they are not quite like anything I've seen before. He makes some solid points about what could help a talent in their quest for an agent.