For 1990-2009 cars

Caution: You can lose control of the vehicle if you try to adjust a manual driver's seat while the vehicle is moving. The sudden movement could startle and confuse you, or make you push a pedal when you do not want to. Adjust the driver's seat only when the vehicle is not moving.

Lift the lever located under the front of the seat to unlock it. Slide the seat to where you want it. Then release the lever and try to move the seat with your body to make sure the seat is locked in place.