you might be doing it without realizing it, DI stands for directional infulence, which can pretty much explain itself, you influencing the direction you go by inputting another direction, so what you do is press the joystick in the direction you want to go, you have to experiment when to use it and which way to go when using it, examples of when not to use it are when you're peach or marth against falcon, do not DI his dthrow because he'll only be able to get a uair on you, it's better than another grab or the knee, and example of when to DI is when you get hit off the stage, just hold the the joystick towards teh stage and you'll live longer