Notice the players around you

Someone in blue means that he has in good standing with the members of his own faction. This could be your enemy. Blue is granted with the abilities to turn in grey to temp you. It is tempting to attack grey without risk, however this is not always the case. If you can stop to attack he current blue one soon enough, you be punished with a full two-minute gray penalty. A healthy does of paranoia can save you in uncertain situation.
Some players like to use the trick to attract you to attack them. They usually do this: run into your attacks while you are fighting monsters. they do so with the purpose of making your turning rogue so that they can kill you without losing alignment. Stay alert and always expect the unexpected.
Threat other players with respect, and they will treat you nice back. Creating a good darkfall environment, which means keep good relationship with player in your clan and allies, is one of key factors to a successful gaming life.