Several functions:

#1: Is the data I am using to analyze the scenario reliable? Do I have the most reliable set of information / can I trust the source? Is this information testable? verifiable? or am I dealing with a (faith) (belief without evidence) assertion.

I do not consider faith a reliable method to determine truth, establish a world (belief) view, or make an informed decision.

#2: A careful analysis of potential loss/benefit outcome. For example: If I purchase this gum ball today, it will cost me a quarter, If I repeat this activity every Saturday (When I lived in Devils Lake I would often walk to the shopping mall with a gum ball machine) I would spend roughly ten dollars a year for an enjoyable gum ball on Saturday that would likely degrade dental health.

NOTE: The loss/benefit analysis is not purely self-centered as if the decision involves a weighted analysis of the potential well being of others and/or our environment

Can my decision actually change anything?

I ask myself if I have all the information available to make the right decision, if not, I do research...

What is in my long term best interests.

No one question can be my only answer to this, as it depends entirely on the circumstance. Each decision has to be made on its merits and there is no formula to any decision making process without full knowledge of the facts.