How can I keep these wall decals from falling off my wall?

[gotbfdk]

We bought wall decals for my daughters room and stuck them to a piece of glass when we moved. Now I have put them on her new walls but they keep falling off. I know they claim to be re-usable, but I don't know if their is a way to get them to stick better or if I just need to buy new ones. Any advice?

[brewdesign]

Clean with soap and water, let dry.

[hj]

Spray adhesive applied to the back of the decal.

[jimbo]

Decals and stickers prefer very smooth surface, like the glass. They are not so happy on a textured surface like your walls.

[leejosepho]

I have forgotten what it is called, but a crafts store should have a certain glue or paste that will hold something in place without being permanent. That is how layout editors used to prepare camera-ready artwork. Or, you might use some double-sided tape.