When it comes to sign placement, it's all about location.
Take this sign, for example:
This is a crude sketch of an actual sign I saw recently. Just some guy offering up some manual labor for cheap. I had no problems with it, except for the fact that a shadow was cast across it. In truth, it looked more like this:
At a quick glance, the sign appears to be conveying a different service altogether. Much like those VAG Construction guys, a bit of foresight in the design and placement of the sign would go a long way.