Speak in tongues - or get a translator
Developers tend to share a quite exact vocabulary and a desire for logical argument, something they rarely have in common with customers. On an XP team, where both have to work together, this can lead to misunderstandings. The way to overcome this is to use a translator: someone the business trusts to explain what the development team "needs to do" in the business terms they are more used to. Often these business terms are purely cost / benefit, such as "invest in testing now to avoid paying for defects later". The corollary of this is that in an introducing-XP-by-stealth situation you need to be prepared to explain what you intend to do (or have done!) in business terms, not in technical ones.