This is a question that Sensei has been asking me a lot lately. Usually after practice when I step up to bow to him. The more I think about it, the more answers I can come up with, and the more I think about it, the higher my bar of standard for myself raises. I've been told I have beautiful Kendo, and when I really think about it, I guess I do considering my level of experience and training (which isn't much). But I always want to strive for more. I never want to lose that hunger to keep progressing, keep learning and improving myself. It's one of the things that drives me in Kendo. I have a definite passion for it, that much I can say without hesitation, and even though I know nothing I continually push myself to take more steps along this path.
The first things that pop into my head, and the things I'm concentrating on most right now, are keeping a straight posture, and making my wrists more loose and flexible. Now, straight posture, to me, doesn't mean rigidly straight back. It means having a "natural" straightness to my stance. We talk about this a lot, mainly when it comes to holding the shinai in kamae and with the legs in kamae. It does apply to many other areas, though. Naturally straight isn't locked in place; it's a relaxed position, with the slight curve (from the kneee, or the loewr back, or the elbows). Things are neither locked in place or bent out of place, they are natural, and, well, straight!
My wrists are an issue that pop up here and there, but I've been concentrating on them for a few weeks now, ever since I was first told that they were too tense. Wrist movement is a key component in a good, fast shinai swing. As it was explained the wrists should bend back as the swing starts, so that the upswing and the wrist motion are all one, not two separate movements. The way I understand it is that on the downswing the wrists should snap out last, kind of like a wave. The energy running from your shoulders, which are driving the sword down, through your arms, to your wrists (which snap forward) and then out through your shinai to connect with the target (Men, Kote, Do). I might be wrong on this, though, so don't take my word for it, but this is how I understand the movement, and it makes sense to me. Up and back, down and forward, power through the left hand, guidance through the right.
Will my thinking change on these areas? I would say most definitely. As I grow in experience, things that made sense before become more refined, until they are entirely different ideas, but for now this is what I know and it has helped me a lot.