They decorate, inform, identify and protect. Decals stay stuck in place. The Rolling Stones tongue logo, a peace sign, a parking permit, university sticker, auto club membership--when it's time to remove them, arm yourself with the right tools. Peel off the decal without having to pick at it, or live with a sticky mess afterward. Both homemade and commercial solutions offer the means to remove the decal without damaging the glass.
Mix 1 tsp. of castile soap or dish soap and 2 tbsp. of white vinegar with 1 cup of warm water in a spray bottle.
Saturate the decal and all of the decal's edges with adhesive remover. Alternatively, spray it with the solution of soap, water and vinegar.
Leave the remover or soapy water on the decal for 20 minutes.
Lift the decal's edges with a card squeegee. Work around the decal from the edges inward. Apply more adhesive remover or soapy water if needed.
Pull on the decal to remove it once you've lifted enough of the decal's edge to get a grip on it. Grab the decal with a dry rag to get a good grip, as the remover makes it oily. If part of the decal remains stuck, hold onto the decal with one hand and keep working the squeegee under the decal with the other.
Apply adhesive remover to the sticky area of the glass and leave it on for 10 minutes. Skip to the next step if you're using soap and water.
Spray soap and water on the glass. Clean the adhesive residue off with a rag.
Apply undiluted white vinegar to the glass with a rag. Polish the glass with a lint-free cloth or newspaper.