The motion of a humanoid robot is one of the most intuitive communication channels for human-robot interaction. Previous studies have presented related knowledge to generate speech-based motions of virtual agents on screens. However, physical humanoid robots share time and space with people, and thus, numerous speechless situations occur where the robot cannot be hidden from users. Therefore, we must understand the appropriate roles of motion design for a humanoid robot in many different situations. We achieved the target knowledge as motion-design guidelines based on the iterative findings of design case studies and a literature review. The guidelines are largely separated into two main roles for speech-based and speechless situations, and the latter can be further subdivided into idling, observing, listening, expecting, and mood-setting, all of which are well-distributed by different levels of intension. A series of experiments proved that our guidelines help create preferable motion designs of a humanoid robot. This study provides researchers with a balanced perspective between speech-based and speechless situations, and thus they can design the motions of a humanoid robot to satisfy users in more acceptable and pleasurable ways.