The most common way is to look for the black hookup wire. The majority of pickup companies connect the black and ground wire to the beginning of the coil. The beginning of the coil is wound directly to the rod magnets in vintage style single coil pickups. Looking at the pickup from the top and the two eyelets are on the bottom left and bottom right of the bobbin on vintage Strat style pickup. If the beginning wire starts at the bottom left eyelet, then the coil is wound clockwise around the bobbin. If the beginning wire starts at the bottom right eyelet, then the coil is wound counter-clockwise around the bobbin. Later on I will show you a trick that you can do with your analog or digital volt/ohm meter. Your analog meter has a pointer or dial that moves to the proper reading where the digital meter has a digital or numeral read out.