The overarching theme of early market engagement is the organisation stating the outcomes it needs to bring about, and suppliers giving feedback on how they might be achieved. All discussions should flow from this theme.
Points to consider
The customer will 'bring to the table' the outcomes they wish to achieve, the main risks and issues foreseen, and how suppliers might be involved
Suppliers will respond with an indication of how the outcomes might be achieved, the risks and issues as they see them, along with feedback on timescale, feasibility and (perhaps) affordability
The key risks should be explored as fully as possible: where customer and supplier see them arising, who should manage them, what the implications are
Discussions on costs should be indicative only, and this needs to be made clear to suppliers
Consider if it is appropriate to disclose information about your own budget.