The best way to begin is to ask the local school district if they have a particular curriculum or program they use for teaching about bullying. Then find ways for your show to reinforce that. Generally, a state has adopted a program. (7 pillars of character education, choosing food by color, etc.) So if you can reinforce that lesson it is good.
At the last school I was at I spoke on Friendship and bullying. I noticed signs on their walls, so I kept pointing out phrases on the signs and incorporating them into the show. The principal reminded the kids at the end, "Now these are things we have been teaching you all year! We really appreciate Mr. Borders for coming and helping remind us all of what a great school this is... etc."
I don't use the word "bully" much at all, especially in lower elementary. They tend to call every act a bullying act then. Some principals have even asked for a bullying assembly without the word bully and I oblige them. I call it Friendship Skills. I do still use my bulldog named Bully Boy. He was a guard dog for a store until they got cameras and alarms. Now he is retired and I need to retrain him.
For any teaching assembly you want it to have 3 or 4 simple lessons that are taught in fun ways. Pick the lessons first.
Example. Have a large arrow on a square sign. When it is pointing up talk about standing up for yourself and speaking up for others.
When it is pointing down talk about avoiding put-downs, and writing down what happened and who was there to see what happened.
Point the arrow to the side. Talk about places to find help if you don't feel safe.
(It could be a spinning arrow, like a game board, with a pie chart on it. When the arrow is up it points to Stand Up/ Speak Up/ Build Up.
Down is No Put-downs/ Write it Down/ Calm Down
Sides is Feel Safe/ Tell someone
So that is one idea. Here is another:
T.E.A.M. Talk it out.
Express your feelings.
Accept others feelings.
Mend the friendship.
I have thought about a Heroes vs. Super Villains show where different puppets have powers that can be used for good. Sense of humor. Strong arms. Quick thinker. But those powers can also be used for bad. So we find ways to help them decide to build others up instead of put them down. Steve Taylor has a Heroes magic trick that is very nice.http://www.stevetaylorpro.com
My main suggestion is that you focus on the positive side of bullying. Main elements are probably
1. I have a right to feel safe.
2. Caring friends can make a difference.
3. Avoid places where you don't feel safe.
4. Choose to build people up, not put them down.