The short answer: experience. It is only through experience that you will be able to reduce the time required to take in raw information, develop a mental model of the current environment, and then decide on the most effective/efficient course of action within that environment.
How do you get that experience?
1. Reading--lots of it. Read everything you can get your hands on related to your operational environment--Law Enforcement. Read the stories of those officers who have already walked the path you are on now. How did they handle their situation? What would they have done differently? Why? I highly recommend that you read On Combat by LTC Grossman, if you haven't already.
2. Study and memorize your operational area/ terrain. Where are the best areas for bad guys to ambush you? Where are the best areas for cover? Concealment? How can you use lighting/ shadows to your advantage? Where are the no-go areas? What are the best avenues for egress?
3. Know your enemy! What tactics do they use? Where do they conceal weapons? What kind of weapons? Know what the pre-attack cues look like. What are the most common attacks on LE? What does it look like when someone is reaching for their wallet? Compare that to what it looks like when they are retrieving a weapon from their waistline or back pocket. What does it look like when someone is concealing a weapon in their hand (palming)? What does it look like when someone is planning on running? In essence, you must become the predator so you can get into his mind.
4. Sand table/ scenario training--nothing fancy. Based on #1-3 above, discuss with other officers what they would do in a given situation (real or make believe). They may have relevant experiences that you can leverage.
How do you make quicker decisions?
1. Experience-- yes this again. Work with your arrest control and firearms instructors. You have to get out of the mat room and train in a real environment. Put yourself through shoot--don't shoot scenarios.
2. Battle drills--what are your tactics, techniques and procedures for dealing with ambushes, officer down, active shooter, etc...You have to know these cold BEFORE it happens. I would also become more than proficient in self-aid and buddy aid. Have you trained applying a tourniquet to your own arm/ leg? Do others on your shift know how to do it?
3. Reduce decision points. Don't learn 15 different defenses or counterattacks to a given attack. Learn ONE, and drill it until you can do it with a blindfold on and a broken arm, while holding your breath. Too many choices will paralyze you.
4. Mindset. Don't think something might happen. You know it will happen--and be ready for it. That 14 year old suspect will assault you/ pull a weapon/ run. The body won't go where the mind hasn't been. YOU MUST UNDERSTAND THIS!
These are only a few ideas.
