Plan the practice before the putting green.
Start with a simple question: what would make you use the green most days? The answer is more useful than picking a shape from a photograph.
Choose the shots you want.
Short putts, longer lag putts and chipping use space differently. Tell the designer which parts of your game you want to practice. A focused layout can be more useful than squeezing every possible feature into a small area.
Think about everyone using it.
A green for individual practice can still work for family games. Consider routes through the yard, places to stand and whether the layout should accommodate several people without crowding the playing surface.
Use contours with a purpose.
Cup placement, breaks, fringe and the overall shape influence the practice available. Discuss the types of putts you want and ask how the proposed layout supports them. More contour is not automatically more useful.
Plan for missed shots.
If chipping is part of the idea, look beyond the green. Nearby windows, vehicles, paths and neighboring property all matter. Decide whether the available space supports that use before finalizing the scope.
Connect it to the rest of the yard.
Keep practical routes to the patio, beds and entrances. Ask how drainage, maintenance and existing landscaping affect the design. Bring photos and rough measurements to the conversation, along with the way you hope to use the space.