How do I keep my camera sensor clean when changing lenses outside?

Changing lenses outside can feel like a risky endeavor. After all, during the swap, your camera's interior will be exposed to the elements, potentially allowing dust, dirt or moisture to land on your sensor. Those resulting spots can be a pain to edit out, extending your editing time. It may also require a sensor cleaning session. While it may be tempting to avoid it altogether, sometimes you need a different lens, and there's no getting around the swap. Sensor spots are unavoidable, but some si...