remain aware of your surroundings at all times. a rule that has and will continue to keep my out of harms way. be aware of your surroundings, the way people are acting (aggressive/overly friendly), and where important objectives are placed, loved ones/anything that can be used as a weapon/position of opponents or possible opponents.
i sound a bit paranoid, but i consider being a bit paranoid a good thing.
Serve no master.