Your choice of words is always important when you are conducting business. The right choice can help you soothe an angry customer, close a sale, or earn a raise. But also important is the speed at which you speak.
If you talk too quickly, listeners may not be able to keep up with you.
If you speak too slowly, they may become bored or try to second-guess what you're about to say.
You should average about 180 words per minute. You can practice with a paragraph from any book and a watch. Count out 180 words of the text, and then practice reading it out loud.