I'll jump into a fight if there are already three wizards, but usually focus on Marleybone or Mooshu. Dragonspyre on my higher wizards. But I notice the fight is often filled with wizards who have shadow magic. You get credit towards badges for any fight you help out with, even if the fight is in Wizard City and you're in Krysalis (or whatever the top world is).

There needs to be badges for helping out on each world to encourage higher level wizards to help out in the worlds where they're questing or worlds close to it.