In addition to all the above, it helps greatly to drive an innocuous color and type of vehicle. An old white
Chevy pickup that had been a water department vehicle served me well in this capacity. The truck had a head-ache rack, side toolboxes and a police spot-light.
Police never gave me a second look. It was very stealth. I have also had similar success driving at speed in an old black
Mercedes 300SD. It is something a grandpa would drive. Police just seem to look past it or through it as though it was not there.
The exact opposite of this has been experienced while driving various sports cars irrespective of their color, year or make.
YMMV