How do you make a decal stay on a window?

To make a decal stay on a window, start by cleaning the glass surface thoroughly with glass cleaner to remove dust and oils. Ensure the window is dry before applying the decal to avoid bubbles. Press the decal firmly onto the glass, smoothing out any air bubbles from the center outward. For added adhesion, you can use a heat source like a hairdryer to warm the decal slightly, which helps it conform better to the surface.