A Mensa Question

My dad sent me a joke this morning that included a little puzzle in it. I have modified it to include just the question. Can you figure it out?

Mensa is an organization whose members have an IQ of 140 or higher. A few years ago, there was a Mensa Convention in San Francisco, and several members lunched at a local cafe.
While dining, they discovered that their salt shaker contained pepper and their pepper shaker was full of salt. How could they swap the contents of the bottles without spilling, and using only the implements at hand?

The answer is in the comments when you're ready to see if you got it right.