If you are doing this inquiry as part of a class or group, share your creations with each other. As each creation is presented, everyone else in the group should take a turn providing constructive criticism that focuses on the harmony of the piece. If you encountered a specific problem in creating the piece, or if you are unsure what you might do to make it better following the constructive criticism, this is also a good time to discuss the problem and collect suggestions and possible solutions from the group.
If you are not part of an inquiry group, share your creation with someone: music teachers, classmates, band mates, friends, relatives, or fans. Request the feedback that is feasible from your audience. For example, a relative with no formal music training may be able to tell you which parts of a piece achieve a particular style of effect, while a music teacher may be able to help you identify why a particular chord progression feels awkward.