Your mouse should be kept as close as possible to your keyboard to prevent excessive reaching.

Most keyboards are set up with the mouse on the right-hand side but left-hand mousing is often encouraged because it:
-Allows the mouse to be closer to you ie you don’t need to reach past the number pad to use the mouse
-Frees your right hand for other tasks
-Is useful for right handers to ‘spread the load’

When swapping from right to left-hand mousing:
-Avoid using a dedicated right hand mouse, use a symmetrical one
-Swap your right and left mouse buttons so that you can use your left index finger as the main selector
-Start on a quiet day when you can have some unpressured practice

Nicola