Start with the client requirements
Building use, occupancy, operating hours, resilience, comfort, energy, maintenance and programme expectations should be stated before systems are selected.
Confirm the building information
Current plans, sections, elevations, structure, fire strategy and existing-building records establish the geometry and interfaces the MEP design must respond to.
Identify surveys and utility constraints
Existing services, capacity, condition, incoming utilities and access limitations can change the viable design route and should be investigated early.
Keep assumptions visible
Where information is missing, assumptions should be recorded, source-tagged and reviewed at agreed decision points rather than hidden inside drawings or calculations.