* Headlights: The adjustment is usually located on the back of the headlight housing itself.
* Clutch: There's no screw to adjust the clutch; it's a hydraulic system.
* Brakes: Brake adjustments are typically done at the calipers or by adjusting the parking brake cable.
* Throttle Cable: This might have an adjustment nut, but its location depends on the engine.
* Seat: Seats have various adjustment levers and mechanisms, not screws.
Provide more detail about what you are trying to adjust, and I can give you a more precise answer.