Explaining Quickly and Clearly

In my job, I have recently had to explain to other people how to do parts of it.

How does one do this quickly without appearing to treat the other person as if he were stupid but still get the important points across?

Over the past four months, I have picked up a number of points that are important. For a fairly simple job, there sure are a lot of them.

It is something like an elevator speech. (How would you introduce yourself if you were in an elevator? (Limited time.))

I have not figured it out totally, but it is an interesting exercise.