Hi Tristan,
Some decisions don't have to be made right away and others do. Either way you should have as much information available to you as possible. The more you know and are aware of, the better. Here's an article I wrote on the very subject
Keys To Making A Good Decision.
If you have to make a split-second decision in an emergency your sub-conscious mind usually takes over and you operate on automatic pilot. I'm sure we've all heard of stories where people react with what seems like super-human strength or courage when called upon in a dire situation or emergency.