A coworker was complaining about the fight with her boyfriend. Instead of telling me "He wanted me to take care of my sick child, even though I hadn't slept for the past day and a half", she basically gave me an itinerary of the child's illness, exactly how much sleep she had, hospital visits, calls to her husband. etc.
Simply put, if you wish to vent to me, just say it succintly, don't go into detail and provide a whole background as if you want to really convince me you've been wronged.
Also, if someone doesn't reply back to your hello, don't bloody assume they are angry at you. Too many people assume other people carry grudges and are angry at other people. Jeesh, I thought I was paranoid.