Because its exact location on the valve cover can vary slightly, the best approach is to:
1. Locate the valve covers: These are the two covers atop the engine.
2. Look closely at the valve covers: Carefully examine them for a small, plastic valve with a hose attached. The hose will usually lead to the intake manifold.
3. Consult a repair manual: A repair manual specific to your 1999 Buick Regal 3.8L will show a diagram precisely indicating the PCV valve's location. This is the most reliable method.
Don't hesitate to search online for "1999 Buick Regal 3.8L engine diagram" to find visual aids. Pictures can be immensely helpful in identifying the PCV valve.