Some good advice from Wired News:
Do not use profanity. Be very careful when discussing financial or business affairs. Avoid any mention of your private parts. Do not offer any guarantees, or refer to checks that may or may not be in the mail.
Refrain from describing anything or anybody as "free." Abstain from the exuberant use of punctuation marks. Shun simple salutations like "Hello," and opt instead to craft a detailed, personalized subject line.
Oh, and don't ever use the word opt, particularly in conjunction with the words "in" or "out."
PR people are running into this problem:
Hughes isn't the only one struggling to communicate about spam. America Online's public relations department recently sent out a press announcement about the company's spam-blocking efforts, and was dismayed to discover that many reporters' e-mail filters tagged the release as spam.
AOL media reps had to send out another mailing asking reporters to visit the company's corporate website to read the release.