Write your decision as a question at the top of a sheet of paper. Word it as clearly as possible.
Draw a small square on the left side of your paper about half way down your sheet. This square represents your starting question. You'll want to have enough room to record all of your solutions.
Brainstorm all of the feasible answers to your question. For each answer, draw a short line from the starting square toward the right. Angle the lines and keep enough space between them that you can add more answers if you need to. Label each line with a brief description.
Decide whether each answer you generated leads you to another decision you must make or whether it leads to an uncertain result. If it leads to another decision, draw a small square at the end of the line. If the result is uncertain, draw a small circle.
Address the decisions in the same way that you did in Steps 3 and 4, drawing lines out from the squares with the possible answers and labeling them. For the circles, draw lines that represent possible outcomes, which can be specific or which can use labels like "best outcome," "moderate outcome" and "worst outcome." Repeat until your decision tree ends in possible outcomes.
Review all of the decision points and results to see if you can locate additional points to add to your decision tree.
Gather data to help you determine the likelihood of each outcome. Then, record the probability of each as a percentage on the outcome's line, making sure that the percentages add up to 100 percent.