shake one's head

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb To move one's head from side to side, in a repeated swiveling motion from the neck, to indicate disagreement, negation, disbelief, or dismay.
• verb less common To move one's head up and down, in a repeated hinge-like motion from the top of the spine, to indicate agreement, affirmation, approval, or simply polite attentiveness.