Make sure the people involve are aware why it is wrong- I know it sounds funny but I am a peer councilor at my school and often some people don't understand it's wrong-
- a joke to some people isn't to others
- play fighting builds up
- little things like name calling is the worst kind of bullying, it builds up inside people until the person feels hopeless/helpless
- etc.
Punishment wise don't go over the top as you could also turn into the bully.
(fighting is not always to do with bullying however deal with it in the same way as fighting- fighting leads to bullying if not already)
Here's a link:
http://www.scouts.org.uk/bullying/index.html