Unwritten Rules that Could Get You Fired:
1. Never Bad Mouth the Boss. (Venting about your boss in any forum is a great way to find yourself packing. A Vice President of Oracle ranted about his boss in an Instant Message and ultimately wound up unemployed even though he thought the IM was private.)
2. Don't disparage Your Companies Products. ( Same issue. Making negative statements about your companies products or services can get your fired. That's true if someone overhears a conversation in an airport or at a party. You represent your company and that's at all times.)
3. Written Communications. (Never put anything in writing you don't want the world to know. It's amazing how often employees put really stupid things in writing -- emails, social media -- and it comes back to haunt them.
4. Disclosing Confidential Information. (Really a good idea to keep proprietary info quiet -- even at home. You never know when a child might pick up on something and let it slip. Disclosing this type of information can cause serious economic damage to your company.)
5. Social Media -- Loose Lips Sink Ships. (It amazes me what people say. Saw one post by someone who was at a conference for her company. She was bored and couldn't wait to bail and get to the bar.)