* Don't talk about your current employer. Work within the company to solve any problems there. (If you can't solve problems there, get away ASAP. Work with a lawyer, if necessary. Still don't talk about it publicly while you're there.)
* Don't name individuals. That's fraught with risks, including you being somehow wrong and doing harm, Internet mobs being dumb as snot, and all the shameless data-mining surveillance many companies are doing could mean outsized/inappropriate harm to someone.
* Don't name a company if you've worked for them, or otherwise had non-public access to it. Who is going to trust you in the future if you don't show discretion.
* Don't violate NDA.
* Be sufficiently vague so that you can talk about generalizable learnings. Your goal is for other people to learn not to do X; your goal isn't to hurt the reputation of a person who once did X. To help anonymize the subjects, you talk about things you've "seen" (in an ambigious sense) at places you've worked, as well as with people you've talked with, companies you've studied, etc., without saying which it was. You can do this without saying anything untrue. This is harder to do with only a few years of experience, though.
* Don't try to unmask anonymous/pseudonymous other people who share, nor unmask the identity of companies/people they're talking about. You could be wrong in your deductions, or you could just be disrepecting how they tried to share with discretion in good faith.
Other guidelines/practices?