The most important thing you can do with any kind of mouse or keyboard usage is not to keep your hand or hands resting on the device.
For example with a mouse always keep your arm free and resting in your lap or wherever. Move your hand to the mouse, move it, click it, then take your hand away. Your hand should only be touching the mouse if you are actually moving it or clicking it. The same goes for keyboards. My hands are nowhere near my keyboard unless I am actually pressing keys. When I am thinking what to type next my arms are folded at my chest.