I found these ways of identifying your time stealers:

Interruptions - telephone
Interruptions - personal visitors
Meetings
Tasks you should have delegated
Procrastination and indecision
Acting with incomplete information
Dealing with team members
Crisis management (fire fighting)
Unclear communication
Inadequate technical knowledge
Unclear objectives and priorities
Lack of planning
Stress and fatigue
Inability to say "No"
Desk management and personal disorganisation