How to effectively stain over polyurethane for a seamless finish?

To effectively stain over polyurethane for a seamless finish, follow these steps:

1. Lightly sand the polyurethane surface to remove any gloss and create a rough surface for the stain to adhere to.
2. Clean the surface with a damp cloth to remove any dust or debris.
3. Apply a wood conditioner to help the stain penetrate evenly.
4. Apply the stain in thin, even coats, wiping off any excess with a clean cloth.
5. Allow the stain to dry completely before applying a clear polyurethane topcoat for added protection and a smooth finish.