if you have big hands and you're using a small-ish mouse a lot and your hands/wrist hurts, i really recommend getting a bigger mouse. it has seriously made a big difference for me
I just purhcased a (large) vertical mouse and it has immediately Changed Everything and I can never go back. Wrist pain ABOLISHED.
A vertical mouse is the only way I'm able to get out of the bad habit of moving the mouse with my wrist and into the good habit of moving it by moving my whole arm.
Switching to a vertical mouse and a two-piece keyboard (I use an ErgoDox EZ) seem to have completely arrested the advancement of my RSI. I still need to periodically flex my right wrist to keep it from gumming up, but it doesn't develop pain like it used to.
For anyone considering trying this: Try multiple models. Ideally, try them out at a store, but this is an imperfect test and you may find that a mouse that fit OK at the store doesn't work so well for real usage. Plus, not all models will have demo units available.