From this box draw out lines towards the right for each possible solution, and write that solution along the line. Keep the lines apart as far as possible so that you can expand your thoughts. At the end of each solution line, consider the results. If the result of taking that decision is uncertain, draw a small circle. If the result is another decision that needs to be made, draw another square.
Squares represent decisions, circles represent uncertainty or random factors.
Write the decision or factor to be considered above the square or circle. If you have completed the solution at the end of the line, just leave it blank. Starting from the new decision squares on your diagram, draw out lines representing the options that could be taken. From the circles draw out lines representing possible outcomes. Again mark a brief note on the line saying what it means.