Tie another small loop in the string just above the intersection of the two cross pieces. This will be the kite's bridle, the string to which the flying line is attached. Make a tail by tying a small ribbon roughly every 10cm along the length of string. Attach the tail to the loop at the bottom of the kite. Spray can glue is really good for patching up paper kites.
Stability is improved by the use of an effective bow and a flexible tail.
Hold your kite up by the string when you are finished to see if it is balanced. You can balance it by putting more paper on one side. Kites are different each time you make one, so slight adjustments might need to be made for each kite.