At the end of the strand (right when the racquet naturally begins to curve), pull the strings tight. You may need to pull on each strand from the base up to get rid of any slack in the string. Make sure the tension in the strings is very high and there is little give when you push down on the strings with your hand.

Tie a knot in the string on the outside of the racquet. Make the knot very close to the racquet for best tension, pliers can help slide the knot down to the frame. More than one knot may be necessary to prevent the string from sliding back through the hole.