Many people may have heard about Ben Franklin’s T: to help reach a decision, list pros and cons and then cross off those that balance each other out (See my post of April 2, 2006 – Franklin T’s and other decision aids.). Some variations on it appear in Len Fisher, The Perfect Swarm: The science of complexity in everyday life (Basic Books 2009) at 143-145.
Fisher says that sometimes a simple tally of how many arguments you have listed for an action compared to how many against will suffice. If you do not know enough to weight the various arguments, just count and decide for the larger number. With what Fisher calls “level-wise tallying” you underline the factors in the pro and con columns that you think are particularly important. Then tally those decisive factors and go.