For email, a simple paragraph explaining what it is and why they should support it.
For in person, a quick summary of the technology and its benefits.
I guess I'll put together my best effort, but I think others who have more experience with this could do a much better job than myself. If we all had this at our disposal and we shared that information regularly at the stores we frequent, that could really move the needle.
I started this thread of "top 100 reasons bitcoin is the best currency today", maybe there is something in there of use for you.
https://bitcointalksearch.org/topic/100-reasons-why-bitcoin-is-the-best-currency-today-338050