How do you find intervals of increasing or decreasing on a graph?

To find intervals of increasing or decreasing on a graph, analyze the function's derivative. If the derivative is positive over an interval, the function is increasing; if it's negative, the function is decreasing. You can also look for critical points, where the derivative is zero or undefined, as these points can indicate where the function changes from increasing to decreasing or vice versa. Finally, test points in each interval to confirm the behavior of the function.