Ensure that student engagement does not 'flatten out' and that students' feel that their contributions are valued and contribute to a more active and inspiring learning experience.
Don't encourage student contribution or engagement in the Class Feed (or elsewhere), if you are not intending to use those contributions for anything.
Our experience is that students quickly stop contributing and sharing if their contributions are not taken seriously by the educator - that is, if the contributions are 'not used for anything'.
We therefore recommend that you always mention what contributions will be used for when you encourage students to share.
For example, if you ask students to share thoughts on topic X ahead of a lecture, you might also mention that the contributions will form the point of departure for the discussion. Then when in the lecture, make specific reference to the student contributions.