Observe your surroundings properly and you can avoid potential trouble. Leave the rest of the OODA Loop aside for the moment and think just about your observation skills. How effectively could you observe the crowd in the photo above? Processing all the inputs in your environment can be daunting task. How can you identify and then keep track of the important things?
You can start by understanding the limits of your conscious awareness: the average person can only capture, process, comprehend and recall 7 pieces (+/- 2) of unrelated information. Unless something happens fast to get the information on the fast track to long-term storage, it will be quickly forgotten. Practice keeping focus on the 5-7 most critical pieces of information you need to make a good decision.
So how can we determine which 5-7 pieces of information are critical to keep in mind?
More: Focusing Observation to Improve Situational Awareness | kR-15: resources for firearms enthusiaists