To win at anything the only thing you need to have is the correct knowledge.

War; the knowledge of the enemy, of yourself, and the battlefield.

Survival; what you can eat and what can eat you.

The list goes on.

What you need to know to survive life however is a knowledge base so broad that no living being in existence could even begin to memorise in any meaningful way to survive in every possible scenario. What a living being can do is find out what the questions will be, and look for their answers before the test arrives.

Research, learn, investigate.

Learn the motives of people, learn how things interact with each other. Figure out what makes the world tick before you go off to engineer it to how you want. Find the outcome you want, find the outcome others want, find what the outcome is if you continue as is.

After you know what others want, after you know what you want, after you know the current situation, calculate. Calculate chances of a gunfight, chances of an ambush, chances of variation in predictions. Chances of survival. If you know what will happen in the future then you can plan, if you can plan you can execute that plan. And when that plan eventually goes wrong you will know what best to do because you already planned for what would happen if you failed. 

It's good to have at least 2 back up plans, especially if your life depends on it. Although know that the average person will make far more mistakes then just 2.