Common Reasons Shrinkwrap doesn't work.

I’m having some problems using the shrinkwrap modifier. I’m watching a tutorial, and following these steps specifically. However, when I try to use the shrinkwrap, nothing happens.

I am trying to use the “project” mode with negative and positive both checked, along the ‘y’ axis.

I’ve checked the normals, and ensured that I am attempting to target the correct object. I’ve poked around the options, just to see if anything would do anything, and the most I could do us severely disfigure the object in question by playing with the settings…no desired effect.

I’ve also ensured that there is no subsurf above the modifier, and that the to-be-shrinked object is above the other object. I just can’t think of any other reason it wouldn’t work.

Are there any other common causes that would keep shrinkwrap from working as designed?

If it helps I’m going through the Kara tutorial from Blender Cookie. Trying to shrink one of the front crest thingies to the vest.

Could you post your blend file?