Start with the business problem
Explain why the website needs to change. Is the offer unclear, is content hard to update, or are visitors struggling to contact you? A specific problem is more useful than a list of visual preferences.
Name your audience and their next step
Identify the people the site should serve and the action you want them to take. An enquiry, a product trial and a purchase each need different supporting content.
Inventory what already exists
Share your current site, brand assets, useful pages, product screenshots and existing integrations. Flag pages that receive important traffic so they can be considered in the migration.
Define the practical constraints
Include an approximate budget, any real deadline, the person approving content and who will manage the site afterwards. These details help shape a realistic scope.