Completely agree with Nari on this. The post I had written was for a on stage/in booth demo at a conference. When you're in front of a customer, the dynamics completely change. There is the usual technical vs business divide and sometimes even different parts of the business. Furthermore, questions can go deeper and the audience is well informed - maybe they've even seen your competition or use a similar software already.
I think that the first thing that one needs to be clear about is the intention of the demo. If you're on stage, the intention is to create a buzz. If you're in booth the intention is to generate leads. If you're in front of a qualified customer, the intention is to uncover the details of their needs through their questions and objections and to establish a functionality match.
Second, one needs to know in advance who would be there in the meeting and their relative importance to the decision. Thereafter, one needs to communicate the agenda that caters to the more important people first. So if its the business people who matter more (usually the case), demo the front end first and take questions. People from tech will ask questions and should be answered in brief before assuring them that the demo will turn to those parts later. Do note the question in a notepad so that they see it.
Third, get to the Aha moment quickly. This doesn't change no matter where the demo is. In a customer demo, people have come to actually see that the "aha" is indeed there. It is this promise of the product that got you the meeting in the first place!
Fourth, ask the customer for the conference room some time before the actual demo. This time is useful for setup and a mock run. Some times the client people will walk in as well even though meeting hasn't started and they would need to be engaged. For example, in a meeting earlier this week we booked the room an hour before the demo. This allowed us to test the link, the webex set up etc. We had a few anxious moments as a server crashed and we lost the webex session minutes before the scheduled start. Server restart and starting a new webex session took a bit of time but in all we were ready before most of the people got together. To add to all this the client CIO walked in during the set up time and one of us had to engage him while others carried out the set up.
Fifth, address the questions that were not completely answered but written down for detailed answer later.
Finally, do have a closing note at the end of the demo. This usually consists of your summary of questions and objections that the customer raised and a question to them about what is important or a priortisation. Once the customer responds, the important aspects need to be addressed - we'll give you details on mail, its in next version, its not really important because the same issue is addressed differently, its there but we didn't explain well etc. And then the next steps need to be decided. I know that this step sounds very obvious but I've seen and heard many cases, where the vendor ended up spinning wheels and going nowhere because he didn't realise at the end of the demo that he had already lost the customer or that he didn't understand what was important for the customer.
Having said all this, nothing works better than actually getting in front of the customers a few times and learning how it works for your product/offering.