Identify what is below
A fixture above a fixed table can sit differently from one over open circulation. Begin with the use of the floor or surface below.
Set the drop from the lived level, not the ceiling alone.
Use ceiling height as one boundary, then work from the people, furniture, and movement below. Mock the fixture's lowest point in the actual room and have the final mounting reviewed by a qualified installer.
Find the critical sight line
Test the view from seated positions, doorways, stairs, and adjoining rooms. The most important line varies by room.
Mock the full body
Represent both the widest part and the lowest point. A single hanging marker cannot communicate the visual weight of a broad or layered fixture.
Confirm the installation
Canopy, cable or rod adjustment, junction-box conditions, weight, local code, and installer judgment determine what is technically possible for the exact product.