BlueM has the right idea if self adhesive. Let me add to that.
Using soap in water is a common practice for self adhesive pressure sensitive decals. In the sign biz just water was enough for most jobs I did. Too much soap could leave enough film to cause failure of adhesion over time even though you squeegee the liquid out. I recommend use it very sparingly if at all.
If you use a small piece of masking tape as a hinge on one edge you can pre-register placement of the decal. Then flip it up, pull the backing, mist the water on not drench, and squeegee down with one gentle but firm stroke. A credit card works pretty well if you do not have a soft plastic applicator.
Advantage of water is if any bubbles get trapped they will permeate out. Air bubbles will not.
Last edited by hd4unm; 02/13/2013 8:59 PM.
