Think about if you were someone working in the corporate world, what kind of voicemail would you like to receive, and try to keep that image in mind when leaving a voicemail.
Set the number of rings you'd like callers to hear before they hear your voicemail greeting.

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."
Don’t give up when you don’t receive a call from lead you’ve reached out to. You will need to make at least a handful of calls, plus emails and texts, over the next couple of weeks to maximize your chances of speaking to the lead. You may find that leads don’t want to speak directly to you but will communicate through text or email. No matter the avenue of conversation, consider it a win when they start conversing with you through any form of communication. Be persistent. If you don’t hear from them after weeks of effort, nurture them through a drip email campaign. All of the effort you put forth to reach out to the lead may not result in an immediate response but, they may call you in six months and that is a win.