Even when you have a boss as nice as Dan Stone ;) (kiss up moment)...you always get a little nervous if they "need to see you in their office"....here's some help:

Body Stance and Posture
Positive:

Physically on the same level (sitting or standing).
  Directly faces you.
  Comes into your office rather than just standing at the door.
  In a group, sits or stands close to you.

Negative:

Does not face you directly.
  Stands and looks down on you. (Ever have a boss who never sits?)
  Places both hands on his hips to create a wingspan. (Even the big guys and gals   who don't need more "space" may do this.)
  In groups, avoids you, sits with others or does not introduce you.

Eyes, Head and Face
Positive:

Looks you directly in the eye.
  Muscles around the eye are relaxed.
  Facial muscles are relaxed. Lips are their normal size.
  Pleasant face and friendly smile.

Negative:

Rapid eye movement, does not look at you; has a cold, glaring, staring or glazed-over   look.
  Blinks more than normal.
  Raises one eyebrow as if in disbelief or doubt.
  Facial muscles are tight; lips thin out.
  Jaw muscles and clenched, and temple or neck veins throb.
  Smile is stiff and forced.

Hands, Arms and Gestures
Positive:

Hands are in view, opened, calm.
  Arms are open (but may be crossed in a comfortable position).

Negative:

Hands are not in sight -- in pockets, or under the table or desk.
  Hands (in sight) are closed or in a fist; fingers tightly clasped.
  Arms are tightly crossed (defensive or protective position).
  Points or wags his finger aggressively.
  Drums her fingers or fidgets nervously.
  Remember, sometimes body language is not about you. Bosses have their own issues   and you might just be in the line of fire. Observe many situations and look   for consistency for the full story.