For Printed pieces, Coroplast & PVC Signs, design in CMYK format at 300dpi.
For all other Signage design, please design in a vector format (preferred) at real size, or design in Photoshop at real size (i.e. An 8′ x 8′ banner would be designed at 96″ x 96″) in CMYK at 150dpi.
When working from Illustrator, vectorize all live text to avoid font issues and embed any linked files before saving out.