Natural daylight is best. 4PM is what the pros refer to as "the golden hour." Everything looks better. No harsh shadows.
Over a railing outside or inside as opposed to someone holding it. Otherwise...fingers and feet show. Sometimes it's cute to think of the quilt "walking" but generally it's not exactly the best look.
Draped over a big chair or sofa. The less background clutter, the better. If animals are in it, avoid shooting straight on at their eyes. Creepy results sometimes.