The vampire locks eyes with the subject and speaks a one-word command which must be obeyed instantly. The order must be clear and straightforward - run, cough, fall, yawn, jump, laugh, sneeze, stop, belch, follow. If the command is at all confusing or ambiguous, the subject may respond slowly or perform the task poorly. The subject cannot be ordered to do something directly harmful to herself, so a command like "die" is ineffective.
The command may be included in a sentence, thereby concealing the power's use from others. This effort at subtlety still requires the Kindred to make eye contact at the proper moment and stress the key word slightly. An alert bystander - or even the victim - may notice the emphasis; still, unless she's conversant with supernatural powers, the individual is likely to attribute the utterance and the subsequent action as bizarre coincidence.
System:
The player rolls Manipulation + Intimidation (difficulty of the target's permanent Willpower). More successes force the subject to act with greater vigor or for a longer duration (continue running for a number of turns, go off on a laughing jag, sneeze uncontrollably).