How do you change the serpentine belt on a Lexus GS 300?

To change the serpentine belt on a Lexus GS 300, first, ensure the engine is off and cool. Locate the belt routing diagram, typically found on a sticker in the engine bay, and use a wrench to relieve tension from the tensioner pulley. Carefully slide the old belt off the pulleys, then position the new belt according to the routing diagram, ensuring it sits properly on all pulleys. Finally, reapply tension to the belt by releasing the tensioner and double-check the alignment before starting the engine.