Our decisions impact us every day, how do we know we make the right ones.  In a PM environment, the decision is often needed ASAP and will generally have indirect influences that we won't even know about until later (unless you have an Amazing Project System in place ;-)

Making a decision is like throwing a rock in a pond, watch the ripples and eventually they will go throughout the entire pond.  The bigger the rock, the bigger the ripples.

Tough decisions often involve a degree of uncertainty.  The key is to follow a process and incorporate a structured approach when making these types of decisions.  

First of all:  make sure you understand how "big" the decision is, and define big.  E.g. how much will it impact your project based on a scale, also how is the probability of it to occur.   

Second: don't beat yourself up later down the road if you find out the decision you made was not the "Perfect One". When we make decisions, we always make the best one we can based on the information available at the time.  It is sooooo easy to critique after-the-fact, which is a good thing but it must be under the correct context, after-the-fact review is called a Lessons Learned.  So ensure you are following a process when completing lessons learned (e.g. not about pointing fingers but about reviewing the process that was used to make the decision and seeing what could have been done to improve it for the next one).

Third:  develop decision process workflows, checklists and templates.
Examples of decision processes at a higher level include: 

  • who makes the decision (the right person)
  • who is guiding or providing insight to the decision (committee, advisors, etc)
  • what information is available at hand
  • how accurate (quality) is the information
  • how well informed will the decision maker be (before making the decision)
  • what is the priority of the decision (how fast, how much resources can be expended to making the decision)

Additional decision processes in more detail include:

  • Identify - did a proper identification occur to clarify exactly what decision must be made
  • Analyze - how much effort was put into the analysis of the decision process
  • Decide - is a clear statement made so the decision is easily understood
  • Communicate - is the decision communicated properly
  • Act - is the decision carried out, then integrated into a system that tracks it

Fourth - ensure the priority is constantly re-visited and understood by all involved
Example: determine priority (how fast and which decision needs to be made).  An example is to differentiate between urgency and importance.  Some great definitions include:
  • An urgent task requires immediate attention and is often performed in a hurried, reactive mode. An example of an urgent task is calming the baby or attending a meeting. 
  • An important task contributes to long-term values and goals and is performed in a responsive mode that leads to new opportunities. An example of an important task is planning the company’s next relationship-building mixer. Important tasks can sometimes also be urgent, but often are not.

For more details about the above, a great link is:
Author Stephen Covey popularized Decision Principles in his book (a very good read) called: