Start with the person on the other side
Describe the visitor in a sentence. What brought them here? What do they already understand, and what might make them hesitate? A site for someone choosing their first accountant needs different explanations from one for an experienced procurement team.
Name the one useful next step
Pick the action that matters most: read a service page, enquire about a project, find an opening time, or explore a collection. Other actions can exist, but the page should have a clear centre of gravity.
Separate facts from ambitions
List the things you can support today. Keep planned services and hoped-for results in a different list. This makes it easier to write confident copy without promising more than the business can deliver.
Describe a feeling with examples
“Modern” is a broad instruction. “Warm colours, compact navigation, and enough space for project photographs” gives a designer something useful. Choose a few references and explain the part you like in each.
Keep the first brief short
Aim for a useful starting point, not an exhaustive specification. Audience, offer, next action, essential pages, and a visual direction will usually reveal the questions that need a second conversation.