Share your tips for swapping lenses here.
A few to get started:
Don't swap lenses around moving people. They always seem to bump into photographer when changing lenses.
If there is any dust or mist on the air... don't swap lenses.
On very humid days... avoid it.
When there are insects flying around... avoid it.
My process... I loosen the cap on the replacement lens and set it upright on its lens cap on a table. I put the lens cap on the lens attached to my camera, then disconnect it from my camera, keeping my camera pointed downward. I set it next to the replacement lens (also upright, standing on its lens cap). I move the loosened cap from the top of the replacement lens to the old lens and then snap in the new lens. Check for tightness... done.