If your friend has fat fingers and always hit the wrong key, then heavier keys can help.
I would highly recommend model M (better than green IMO)
If your friend cannot touch type, then the only thing can help is practice, practice and practice. There are several online typing tutor websites. I hear that some people benefit from using blank keycaps, but after you can touch type blank keycaps will be a hinderance for everyday work where you use one hand with the mouse and the other hand to hit some short cut keys or action buttons.
If you just want to type sentences effectively using the computer and don't care about learning to use the keyboard, google voice input is very accurate. The paid solution dragon talk is also highly regarded, but doesn't work well if you're not a native speaker or have an heavy accent.
HTH