Almost everything in decoration is taste. A handful of things are not, and they are the ones that make a room look either resolved or slightly wrong in a way guests cannot name.
Rugs go under the front legs of the seating, at minimum. A rug that stops short of the furniture shrinks the room and makes the seating look like it is standing on a mat. Pendants over a table hang so the underside is 75 to 85 cm above the surface. Art hangs at 145 to 152 cm to the centre, unless there is a sofa under it, in which case the bottom edge sits 20 to 25 cm above the back.
Then there is the one nobody applies: a room needs an odd number of light sources at three heights, and at least one of them at eye level or below. That single move accounts for most of the difference between a hotel lobby and a home.