Watching Golf Swings

There's alot of different angles that you can view the swing from.  The two I like most are either from side on or down the target line.  When I teach, these two angles are the ones I spend the most time watching from.  Below is a checklist of what I'm looking for when watching from each angle.
Target line view -
- Set up (body alignment and aim)
- Angle that the club swings back and through as well as angle of the clubface
- Angle that the body turns back and through
- The curvature and trajectory of the ball flight

Side on view -
- Grip
- Width of stance as well as ball position
- Pivot of body back and through
- Head position throughout the swing
- Foot work

From these two angles I'll spend 90% of my time watching the target line view and 10% watching the side on view.  The reason being is I want access to the angle of the swing, the trajectory and curvature of the ball.  Don't get me wrong, everything I listed above is important but I'm able to make much more accurate corrections when I have access to those three things. 
Whether you're teaching or just watching golf swings, you'll get the best view when you focus on these two angles.