The shorter and more memorable your hashtag, the more effective it will be! Your hashtag should contain no more than 20 characters, and should include your competition or project name, or be related to the subject area. Also, avoid using punctuation marks and stick with letters and numbers only.
Examples of previous hashtags include: #spacepoop, #abundantcleanenergy, #IGNITEyourMApp
This way, you can easily see when others are posting about your challenge on a variety of social media channels.