Look at the back of the carpet. The machines make a uniform warp-and-weft grid that looks entirely different from the varied and slightly wavy warps and wefts of hand-knotted carpets.
Again, by looking on the backside of the carpet, note the tightness of the weave and make sure the design is as clear on the back as it is on the front. This are indications of handmade qualities
A master designer and weaver will sometimes sign their rug. Their signature, and sometimes the date, will be incorporated into design in the middle of the upper edge of the carpet.