Be very gentle when you pry each one off. On some keyboards, larger keys like the space bar cannot be removed, so don't use excessive force to try to pop them off. You don't want to end up with a dirty and broken keyboard!
If the water is too hot, it might melt the keys!
Lay each key on its side so none of them are touching. If the keys are laid flat, water will get caught inside.
If you're having doubts about a key's placement, plug the keyboard into your computer and push on the sensor to see which letter corresponds.