"Missing Word" technique is a process that will assist you in keeping your customers engaged. If another person can finish your sentence, then that person is paying attention. For example:
"There are only two things that prevent us from doing something; time and ____________". If your client fills in "money", they are listening to you.
Review your presentation and find places you can use missing word technique in at least 3 places. When customers participate in your presentation, you have a greater chance of success.
For more on this technique, try the book below.