Make a room-by-room record
List the openings and note their purpose, style and any difficulties with the existing arrangement. Include the direction they face within the room, furniture nearby and the desired relationship between privacy and the view.
Photographs can support those notes, but they are not a substitute for a measured survey. Keep early ideas separate from dimensions that have been professionally confirmed.
Keep glazing and frames together
The glass is part of a larger assembly. When comparing options, look at the full proposed window or door rather than treating a pane or a frame as the whole product.
Ask what the quoted specification includes and what requires a separate decision. Finish, hardware and opening layout should be explicit so that changes are easy to identify.
Plan the practical sequence
A project involves access, room preparation and the treatment of the surrounding surfaces as well as the new opening. Clarify how those parts fit together before work begins.
Retain the agreed specification and any product or maintenance information. A clear record is useful after installation, when a finish, adjustment or replacement part needs to be identified.