I just finished listening to the "Eight Minute Rule" cast and though I'm not interviewing soon, I was struck by how much of the advice applies to doing presentations to clients or potential clients. Think about it, if you're going to try to bring in a new client, you're simply interviewing for a job on behalf of your organization. And with existing clients, I try to keep the mindset that all my actions work to either the credit or discredit of my organization, so it still holds.
I brief stakeholders across my assigned region (five states) on a government program with the goal of gaining their participation (read: sales). Whenever I do anything with a new stakeholder or at a new physical site, I follow all of the advice for the eight minute rule as far as driving from the hotel to the location, doing research on security, parking, etc, and planning for the inevitable intervention of Mr. Murphy.
As far as eight minutes, that doesn't hold for me. I usually plan for 15-20 so I can get set up in the conference room prior to the briefing and deal with computer/projector issues. This isn't always possible - I usually get my escort from reception five minutes after the meeting was supposed to start and don't get started for another 10 - but I'm always there in case the ideal situation actually works out.
But I can't stress how important the other prep work is. Being a high D I get a little wrapped around the axle about "wasting" time, so sitting in the car for 20 minutes because I hit every green light, that construction from the night before cleared up, and miraculously found a parking space right away can make me a little crazy. That's where the beauty of smartphones comes in. I can use it to do some emails or (better) to do a quick scan of local and national events so I can make decent conversation if need be.