Meryl K. Evans and Hank Stroll at MarketingProfs have a nice little piece 0n how, and how much, you should follow up with potential customers. There's a point at which endless follow-up with no response from the prospect becomes stalker-ish.
A question they don't answer - how many times do you keep trying when you get absolutely no response? To me, more than 3 or 4 attempts, and you need to call it dead. If someone won't even answer an email, they're probably not going to talk to you.
The tips on how to follow up to make those couple of attempts valuable, however, is quite good. The basic message: say something interesting. In that quick voice message or email, say something that makes the prospect think that talking with your will pay off.
So instead of "I was just following up on that email," try something like "I'd love to tell you a little bit more about how Acme Services has helped other companies streamline their Whiz-bang Process."
They do recommend something that makes me a little nuts when I'm on the receiving end, though:
Another reader says people love to talk about themselves. So try, "I'd like to learn more about your situation." Something about the words, "your situation" gets people talking.
This always sounds to me like, "I'd really like you to do my homework for me, so I can figure out how to sell you something." Sorry, I'm too busy for that. You do your homework, and then call me with specific questions. In the next paragraph, they touch on this:
Do your research before calling anyone. Don't just call people because they're all in the XYZ business. Researching helps identify prospects' needs so you can focus on those when contacting them. A reader suggests trying out message variations as well as using a friendly voice.
Saying, "I know that a lot of marketers are having trouble determining whether they're getting any activity at all from Second Life programs, and was wondering if you've experienced that problem too..." at least sounds like you know who I am, and have some idea what I might be doing.
No matter how great your messages are, however, some people will just never, ever want to talk to you again. There's a point where you have to gracefully accept that, and put them on the back burner - perhaps in line for a quick, unintrusive follow-up email a few months down the road.