You should match the type of engagement to your:
• mandate
• phases of engagement and objectives
• stakeholders
• methods.
If your mandate is an open, transparent and participatory process but you want to ensure diverse representation, you can invite stakeholders that hold different views and fit different demographics to participate. To do this you need to collect demographic data and progressively evaluate who is participating. Look at where they come from and the diversity of views received against your metrics of success. With this knowledge you can progressively refine your approach.