Fill a bucket with 1 gallon of warm water. Add 1 cup of household ammonia to the bucket.
Dampen a sponge in the diluted ammonia solution. Wash the walls with the mixture, beginning at the bottom to avoid drip lines. Remove dirt, dust and any stains that will prevent the stickers from adhering to the wall.
Dry the wall surface with clean cloths. Allow the wall to air-dry for 24 hours to ensure all moisture is gone.
Apply the self-adhesive stickers to the wall according to the manufacturer's directions.
Use a sticker-adhesive glue from the hardware store to help adhere stickers to textured wall surfaces. Paint the extra adhesive onto the back of the sticker. Press the sticker onto the surface and allow it to dry.