Sod is a living plant that should be installed between 24 to 72 hours after it is first harvested from the farm field. The best indication of freshness is soil that is moist (not hard and dry). The grass blades should be dark green and cool to the touch.
Strength of sod can be tested by holding a piece by its narrow end and raising it overhead, without it tearing or falling apart.
Uniformity of texture, mowing height and overall quality, can best be determined by placing several pieces on the ground and looking for extreme variations or visible weeds.