Depends on your goals, imo. I've tried a myriad of different techniques and I will say that there is no one technique that will continually improve your IIDX ability without fail. My suggestion to you, or anyone wanting to improve, is to switch up your technique constantly (sort of like P90x). My tips are based on experience and other peoples' advice:
-I think some songs require ridiculous amounts of stamina and so playing for long or extended periods of time may be beneficial towards that end.
-Some of the best advice I've read about improving your ability to pass and to score on songs (ie: overall ability) is to just
go with the flow of the song. Easier said than done, I know, but if you just break each song down into parts (or measures) and just focus on matching the bpm, you should see some definite improvement.
-Sometimes I like to just visualize the pattern I'm supposed to do by looking at the keys and thinking about the rhythm. Sort of like treating IIDX like an instrument, I guess. Imagine if someone were sitting next to you and told you to repeat this pattern on the controller while looking at the keys: you would more than likely be able to do it without the pressure of the game. Practice that enough times and soon enough you'll be able to apply it.
-If you're trying to learn tricky rhythms, a friend once told me to literally just 'throw your hands down' on every note (probably b/c he's a big Pop 'N player). I don't know why, but this worked for me.
-Learn NOT to look at your bar and focus just on the notes as they're coming down. This goes without saying, but it's a lot harder to apply than you think.
I stated in another thread that I only recently cleared my first 12, and I've been playing IIDX since about 5th Style, just to give you an idea of how long it's taken me to improve. Kind of sad, to be honest, but IIDX has a very rewarding aspect to it when you're able to clear new songs and improve scores...I think that's why it has the kind of fan-base it does.
Some of the techniques I just stated may seem strange, but hey, some things work for some people and not for others. Just find what works for you.
I only wish someone could give better advice about how/when to incorporate your thumbs b/c I'm having problems breaking the next barrier because of it..
