For the verbally disruptive:

These are the “mouthy” ones.

• First you can't let them get your goat.
  
• It may be that you can encourage positive mouthing-off and ignore the negative.
  
• Give them special attention in other ways.
  
• Establish a good personal relationship so you can ask them privately to tone it down in group sessions.
  
• You can look at them blankly for an uncomfortable length of time so they know they were disruptive without having to call them down.
  
• If they are a diagnosed “Asperger” and you have a good relationship with them you can simply and directly tell them to let others to speak – they need direct instruction not hints or subtle cues.