1.) Good design is key
This ad for Jack Daniels on a London cab be easily seen from skyscraper windows and it looks classy and interesting from the street. A great combination of good design and creative positioning.
Another example from the UK, this wrap for a printing company is loud enough to get a lot of attention but understated and elegant enough to convert viewers into customers. This design is stark contrast to the huge-text, in-you-face, explosion-and-fire designs of most commercial wraps on the road. No one has ever been annoyed into becoming a customer.
Good design in vehicle wraps is surprisingly hard to find. A clever, well-designed vehicle wrap is an easy and immediate way to set your ad campaign miles ahead of everything else out there.