The clutch cable for motorcycles and some manual transmission-equipped cars can be adjusted by tightening or loosening a "knuckle" nut on the cable in one of three locations. The cable is adjustable at the circlet where it enters the clutch, at the attachment to the clutch housing through which the cable is threaded, and where the cable connects to the clutch pedal or handle.
Unless other parts obstruct your view of and access to the clutch cable, the only tool necessary for adjustment is an adjustable wrench. The most common place to adjust the cable for a clutch that is slipping is at the clutch housing, since it does not involve disconnecting or removing the cable. If the clutch is not fully engaging, the nut on the pedal/handle side of the cable should be tightened or turned clockwise. If the clutch is not fully disengaging and the vehicle moves in neutral, turn the nut near the clutch housing counter-clockwise.
At the circlet where the cable attaches to the clutch, make further adjustments by removing the retaining bolt or pin and rotating the circlet to make the cable tighter or less tight. On most vehicles, pull the circlet away from the clutch, turn it, and push it back in.
Adjusting the clutch cable at the pedal or handle allows you to change the feel of the clutch, and involves tightening or loosening a nut. This adjustment enables you to change the distance the pedal has to travel if the driver prefers pushing the pedal all the way to the floor. Start the vehicle in neutral, and carefully shift to check the clutch's new adjustment.