Whatever you do, do not kill off a character for the main reason that you get tired of them or just for the sake of making your readers sad. It is possibly the worst thing to do, because you'll make it seem like the character is worthless and just a waste of space or time.
  One of the main reasons of a character death is so the plot progresses. Whether the other people want to get revenge on the killer, or are encouraged enough by the sacrifice to continue their journey/goal, never X-out a character just for getting rid of them.