How to kill a character on stage without it looking silly

Depending on how you were to kill a character I'd say, its all about getting the timing right, and using sound effects without it looking silly make sure your actors/actress is doing there job. If they are good at their job they won't make it look silly :)

You got to make sure you have a realistic prop for example if you were too shoot someone. The gun needs to look real and work like a real gun without the bullet obviously! Your sound effect would have to be beliveable and effective! And the person your shooting could have some type of pipe under his clothes with fake blood in, the pipe would have a pouch of blood attacthed when this person gets shot how ever you make this pipe work needs to be fast so when he gets shot he could be slyly holding something to press to make the blood come out were he gets shot,remember this is theatre and we can make anything look real. And obviously the actor would have to not just get shot and fall without a fuss he's just been shot he will be in a lot of pain and blood will be everywere, Look up some movie shots of this type of thing see how they do it and react, the actors have to make it look real with the help of us techies doing the rest such as sound effects. You have to get your timing right working together as a team the killer and sound guy need to get the gun shot sound right, and the person who gets shot clearly needs to time how long would a bullet take to get to him the minute the gun is pulled, You should always research and get ideas of how to do things. This isn't the hardest things to do in theatre. If you make it look real we will believe its real.