If your range hood has a glass panel, it should be cleaned often to remove grease and make it sparkling clean. A range hood collects a great deal of vapor and grease from cooking and routine cleaning is a necessity.
Step 1: Prepare the Area
If possible, remove the glass from the range hood. Check on the inside of the hood for clips or screws that hold the glass in place. If you have the owners manual the instructions for removing the glass for cleaning will be in there. Lay the glass on an old towel on a flat surface for cleaning.
If the glass can't be removed, then cover the entire stove top with a drop cloth or towels to collect any cleaner drips. This could make a another mess for you to clean up.
Step 2: Cleaning the Glass
Mix a tablespoon of dishwashing liquid to about a gallon of hot water and use the nylon scrubber dipped into this mixture to scour away a heavy grease buildup. Wipe away occasionally and apply more as the grease loosens.
After you have removed as much grease as possible, use the window cleaner and rags to finish the cleaning job. An ammonia based window cleaner will be more effective for this process.