One of the initiatives that I'm proud and privileged to be involved with is the Sciencewise Expert Resource Centre. There's a team of Dialogue and Engagement Specialists (DESs), and we provide mentoring and advice to government and semi-government bodies which are engaging the public in discussions and deliberations on science-related topics. Sciencewise has asked its DESs for insights - key things we've learnt from experience. This is mine.
Essentially the message is this - when you've engaged people and asked for their views, you need to let them know how your decisions and plans have changed as a result. Or, if you haven't changed aspects that they wanted you to, let them know why not.
This is simple and perhaps obvious, but frighteningly often isn't done well at all. Read the insight to see what happens when it is done.