What has been said so far is pretty spot on, you need to practice practice practice. It’s like learning any other skill you might want to be a master at.
First things first, Knowledge is Key. So spend time watching tutorials, reading forums, reading Yo-Yo related literature, maybe some self help books to overcome limiting beliefs and any mental stumbling blocks you may encounter. Yo-Yo’ing can be a good tool to expand your awareness and mental aptitude.
Second, put what you learn into Practice. You have to BECOME to DO in order to HAVE. But first you got to believe that you can BE. I don’t think the “BE-DO-HAVE” formula was suggested yet but, it drives the point home that you have to Be It, then you have to Do It, and then you’ll Have It. That’s why constant repetition is really the only way to learn new tricks and enhance your skills.
Third, repeat over and over again. Constant repetition of learning and practicing over long periods of time is the only real necessity to get to the level of Yo-Yoing you desire. It is the constant repetition of the motions, the maneuvers, pops, flips, gyrations, saults, and on and on that build it With-Inward into Applicable Knowledge backed Skill that can be expressed With-Outward.
A good amount of your favorite music going on in the background may help you get there as well, so create a play-list of your favorite tunes and try to knock out 2-3 hour sessions a day if you have the time and stamina. It would be the same thing if you were trying to become body builder or working out.
“No Pain, No Gain”??