Hi Mollie! A Hairdryer can help. The heat slightly melts the adhesive making it easier to remove.
Try a hair dryer. Heat will loosen the adhesive.
WD 40, GooGone, warm wet cloth --- depends on what the decal is -- paper, vinyl, etc.
Goo Gone is our go to! :)
WD40 never lets me down! Spray a generous amount, wait 5-10 minutes and carefully scrape it off. Repeat the process if necessary. Good luck!
A homemade substitute for Goo Gone.
Mix together two tablespoons vegetable oil and three tablespoons baking soda into a paste in a small, sealable container. The mixture is usable until it's gone and doesn't include any harsh chemicals or smells.