Eric Barker includes some great examples from the book of how we make bad decisions with careers, business, our jobs, and our personal lives.

Eric summarizes the framework for making better decisions by recognizing the four key challenges:

In their book, Decisive: How to Make Better Choices in Life and Work, Chip and Dan Heath lay out the four key problems that lead us astray when making decisions:

• Narrow framing: Exploring few options. Seeing issues as a binary (Yes/No.)
• Confirmation bias: Only seeking information that supports your beliefs and discounting what disagrees with them.
• Short-term emotion: Letting a temporary mood affect a longer term choice.
• Overconfidence: Being way too sure you know how things will turn out.

By being mindful of these challenges, we deal with them scientifically:

1. Widen your options.

2. Test your assumptions.

3. Get some distance to detach from emotions.

4. Think about what could go wrong and be ready for it.

Further explanation and detail are in Eric's article, which I recommend:

http://www.bakadesuyo.com/2013/04/secrets-making-decisions/

If you haven't already, check out The Four Agreements as well. It's a different take on some the the ideas listed here. I've read it myself at least 5 times & I'm probably due to do that again. LOL But also I've purchased it for at least 10 friends, it's just a lot of those simple things you already know but sometimes need to be reminded of. http://www.businessballs.com/thefouragreementsdonmiguelruiz.htm

This one?

http://www.amazon.com/Four-Agreements-Practical-Personal-Freedom/dp/1878424319

Top review says:

The Four Agreements are very simple, but very profound. To embrace and live each of the Four Agreements is to find yourself experiencing personal freedom--possibly as never before. The Four Agreements are:

Be Impeccable With Your Word: Speak with integrity. Say only what you mean. Avoid using the word to speak against yourself or to gossip about others. Use the power of your word in the direction of truth and love.

Don't Take Anything Personally: Nothing others do is because of you. What others say and do is a projection of their own reality, their own dream. When you are immune to the opinions and actions of others, you won't be the victim of needless suffering.

Don't Make Assumptions: Find the courage to ask questions and to express what you really want. Communicate with others as clearly as you can to avoid misunderstandings, sadness, and drama. With just this one agreement, you can completely transform your life.

Always Do Your Best: Your best is going to change from moment to moment; it will be different when you are healthy as opposed to sick. Under any circumstance, simply do your best, and you will avoid self-judgment, self-abuse, and regret.

Yes, its a quick read, but like I said an often one as well. Being human and all...I tend to slack at times. 

And this one is good too for budding entrepreneurs...& what not to do. http://www.amazon.com/Its-Your-Business-Techniques-Entrepreneurs/dp/1468042785/ref=sr_1_2?s=books&ie=UTF8&qid=1365051882&sr=1-2&keywords=mickey+gorman

Is the essence to do as little as possible, and make sure everything you do is important?

Of which one?  Although, I supposed it could apply to both in some sense. You know the saying... less is more. Which isn't always true, but I guess more a matter of perception, particularly your own perception. Doesn't work so well with A types

Even A types would agree that it's important to focus on the most important thing.

Yes but the key is finding the ability to recognize if this is really the most important thing, or just the most important to you at the moment. Because being chronologically ordered or color coded my not be the most important thing, but for an A type it very well could be in that moment in order to get it done ;) Maybe that's not so much A type but more a little more OCD, ADD, hyper-focus? Or maybe it is just something simple like a term my uncle often uses... "Crazy as a shithouse rat" whatever that means...LOL