If the situation is complex and involves lots of choices and options then use your conscious mind to acquire all the information you need for making a decision. But don't try to analyse the information with your conscious mind (rational thinking). Instead distract yourself by engaging yourself in something else or take a break while your unconscious mind digest it. Whatever your intuition or instinct then tells you is most certainly going to be the best decision or choice.
On the other hand If the decision is trivial or doesn't involve much choices and complexity then it can be handled through logic and taking all variable (options) into account.
The gist is when the situation is complex and involve lot of choices (variables), its better not to think much about it and go by your instinct. And If the situation is simple and doesn't involve much choices then its better to make informed decision rather than rely on instinct (emotions).
Well it does sound bizarre But let me assure its worth give a try.
Another thing which particularly grabbed my attention is concept of "Loss Aversion". It is a mental defect which we all suffer from. We get so determined to avoid any option associated with loss that we are willing to risk lose everything. The thought of loss can be really dangerous and can trigger a dangerous set of feelings where you find yourself taking risk your probably shouldn't take. At such times it is always better to think or take a break before making a decision.
At last Jonah Lehrer word of advice, The best way to make sure that you are using your brain properly is to study your brain at work, to listen to the arguments inside your head. whether these arguments are repulsive or antagonistic to what you believe. still let them have a say. Then only you can make a better and informed decision.
I highly recommend this book to all who want to know how conditioning of brain can help them in making better decisions.