Typically files are designed at 1"=1' at 300 to 400 ppi.  CMYK.  Common software used is Adobe Illustrator, Adobe Photshop and sometimes In-Design.  Corel is also accepted as well as .eps, and .pdf.  JPEGS for photos are adequate, and typically logos should be vector.

You will want to use high resolution images, and provide any and all fonts, if not creating fonts to outlines and/or shapes.  It is preferred if all images are included in the build file, however if not, it will have to be embedded.

Pantone callouts can be used and will be matched as close as possible.

Files do not have be designed with bleed, however, if the designer wishes, they may do so with the standard .5" bleed on all 4 sides.  No critical text or portion of photos / logos should be in the bleed, as it will not be seen from the road.