With a separate keyboard, with any issues, I'd turn it over and knock on the flat side with my knuckles to get the accumulated crumbs and other stuff to drop out - frequently fixes the problem. With a laptop, that's not practical, so going over the keyboard with Canned Air - or PC Duster (trade name?) will usually get the stray particles out of the way. The biggest culprits are stray staples and paper clips.
Fred Wagner