This exercise is really easy and super fun! It's a great tool to have when improvising and can get you around the neck in so many different ways.
You can use several different 4 note and 3 note patterns to vary the rhythm and get different melodies.
Practice this by applying simple singing melodies like 9lb Hammer or Will the Circle Be Unbroken to it, and see what you come up with.
Have fun, and I'd love to hear how its going in the comments!