Think through what you are going to say before you place the call. When men hear the beep, they often freeze up and forget what they wanted to say. If you want to be the go-to guy at work, then you have to exhibit competence on all levels. Don’t spoil your confident image by hemming and hawing and filling your messages with “uhhhhs,” and “ummmms.” If it’s a really important call, consider writing out what you want to say beforehand. If the person picks up, great, you now have some notes to remember what you wanted to talk about. If they don’t answer, you can leave a clear and concise message.
If you sound too relaxed or overly familiar, you're going to undermine both your and your company's credibility. People want to buy from an expert — not someone trying too hard to sound cool. So avoid coming off as too laid back and using too much slang, "um's," and "yeah's."

But it appears I’m not alone. Here’s a portion of one reader’s letter; see whether you relate!
Phrases like, "Please call me back when you get this," "I'm really looking forward to hearing from you," and "Call me at your earliest convenience," are pushy, aggressive, and borderline desperate.