when you tune the instrument a small tip if you want a firmer lock at the peg.Irrespective whether sharp or flat DETUNE the string and wind upwards to the desired pitch. Tension adjustment in ascending degrees of tension is a common sense method of having the gear of the tuning key to stay in one place. Also the little screw that holds the head of the tuning key to the shaft must be tightened to not have any slack.Hope this is of use :).