Please remember to listen to your potential customer's questions and make sure they are all answered clearly. Repeatedly interrupting someone when they are asking important questions does not provide confidence in your offerings or the respect you desperately need to close the deal. This goes double for big-ticket items and long-term contracts.
If you have already made the mistake of interrupting or talking over your customers, you can avoid further embarassment by avoiding the following:
If these topics are more interesting to you than understanding your customer's needs, how will they ever trust you to meet them?