Count the people, not the cushions
Begin with an empty sofa and sit in every position people actually use. Notice the corner where someone curls up, the arm used for reading, and the middle seat guests need. Add a cushion only where it supports an activity or softens a hard edge. A photograph full of pillows may be attractive, but moving a pile to the floor every evening is a sign that the arrangement belongs to the photograph.
Choose one connecting detail
Mixing covers works best when something repeats: a muted color, a woven texture, or the scale of a stripe. Take a photograph of the sofa fabric in daylight before shopping, and compare samples against it at home. Try one larger cushion at the arm and a smaller one in front rather than stacking several equal squares. Leave a plain area of upholstery visible so the fabric itself still contributes to the room.
Make the arrangement washable
Read the cover and insert care labels separately; a removable cover does not mean every part has the same washing method. Choose closures you can open comfortably, and check that replacement covers fit the actual insert dimensions. Keep a spare cover for the cushion used most often rather than buying a whole spare set. Finish by sitting down with a drink and a book. If you immediately remove a cushion, leave it out of the arrangement.
