From the September 2010 issue of Entrepreneur

Social networks can be great communications tools­­--but make a misstep and you could end up doing your company more harm than good. Perhaps the biggest mistake businesspeople make is posting while in the wrong frame of mind. PR man Cas Purdy of Guidance Software in Pasadena, Calif., has a rule of thumb he says everyone should live by: "Don't Twitter while you're bitter." Of course, there are plenty of other mistakes that social networkers make each day. Here's what to avoid. --Ericka Chickowski

Don't Do
Push out political rants because something in the news really ticked you off. Engage friends and followers in political discussion relevant to your industry.
Mingle personal announcements with marketing messaging. Create separate accounts for personal friends and for business associates.
Focus on hard-selling your company's products or services. Consider posting relevant opinions, links and photos about your industry that will truly interest friends and followers.
Automate cross-posting of the same content across numerous channels. Tailor your strategy to the proper channels to avoid annoying Facebook users with Twitter hashtags and Twitter followers with incomplete tweets.
Impulsively air grievances with customers, partners or even competitors on a public forum. Take time to think before putting up content that could be referred to by search engines even after you've deleted it from your account.
Leave your friends and followers hanging when they comment on your links or give you a shout-out with an @ message. Make an effort to engage frequently with friends and followers rather than just foisting your marketing message on them.
Let your accounts lie fallow. Try to offer new content frequently. If you don't have time to commit fully to all channels of social media, think about focusing on one where you can go all out.