HBR has a nice little piece on using statitics that is very applicable to anyone undertaking measurement for communications or marketing. The central tenents are:
Know what you know-and what you're only asserting
Be clear about what you want to discover
Don't take causality for granted
With statistics, you can't prove things with 100 percent certainty
With statistics, you can't prove things with 100 percent certainty
The last one is important in communicating upwards to management. Does anyone care you increased coverage 3.2%? Probably not.