This might seem strange, but many times, you can find out a lot about the person you are calling by their voicemail greeting. Make notes of these things, and follow any instructions they may have requested of the caller. If they say to email, do that; however, send them a teaser email, and ask them to get back to you by phone or email. Do not give them all the information in the first email, as you will lose any chances of explaining your service or product in detail that would meet their needs. If they report being only available at certain times of the day, call back at the requested time.
–Aaron Montgomery, 2 Regular Guys, MontCo Consulting