Define the unit being sold: activities, assets, people, contracts and dependencies. A division's performance within a group may differ from its performance as a standalone business.
Plan continuity on both sides of the separation, including services or resources that are currently shared. Clarify the reason for selling and what the proceeds would enable. Price depends on the transaction's scope and conditions, not simply past results. Organising these questions can be useful before any negotiation and may reveal whether separation is operationally viable.