Remove any dirt or debris from the window using a soft-bristled brush or vacuum cleaner.
Use soap mixed with warm water and a soft cloth to wipe the window frame and glass pane.
Immediately dry the window with a soft dry cloth to avoid streaks.
If you notice any stubborn stains on the glass pane, you can use a commercial glass cleaner to remove them.
Inspect your fixed casement window for any damage or wear that may need repairs.