When i do practice, I tend to think in general terms. Don't use the shoulders to raise the arms is the main thing for me. There are a few other things I play around with though, and I'll try to organize them here.
I should begin by saying that I haven't been a good student for quite some time and that I have only the most superficial understanding of anything (whatever I might be said to actually have an understanding of) to begin with.
On the whole, my focus is on balancing tension where ever I notice it, and trying to have a full, relaxed feeling.
Right now I begin by trying to have a strong extention along the vertical axis (spinal alignment); a feeling of "good" posture, reaching up through my crown and down through my perinium. So I start with an attempt at having a full sense of vertical expansion ("expanding my central column"). For this I try to reach up with my crown then "dangle" my body from it, then I bounce back and forth between this dangling feeling and the pushing up from the hips/legs feeling until I can have a sense of both at the same time, some times better than others. I also try to have a feeling of "sitting back within myself." Once I'm satisfied with the relaxed and expanded feeling I'll start playing with powering my arm movements by it, using my legs to lift and drop the column for cutting and raising movements, trying to use momentum more than muscle. I do a kind of "reverse furitama" where I reach through my arms and fingers and try to raise them with that up and down movement of my central column, usually bouncing my arms off my body (tricepts bouncing off chest area). For this I try to feel like my hara leads the movement: hara up pushes arms up, hara down pulls arms down. I try to time it right so I'm pulling down before gravity does.
For my upper body more specifically, I constantly try to feel my shoulder girdle pressing down until I get a sense of it resting on my spine/central column (and keeping it firmly resting there as much as I can, since once I start moving it tends to not rest "down" quite so well). I try to have my shoulders balanced with respect to the spine (e.g. my left shoulder and chest area droops and is somewhat concave compared to my right side). I try to keep my humorus drawn into the shoulder socket and pay close attention (as close as I am able) to whether or not it's being seperated. I also try to feel all the way around it at the same time. In fact this is the basis for my meager practice: sequential feeling of contiguous lines and areas. If I feel for my shoulders as I practice cuts, for example, I notice I'm usually just feeling portions of them; some more than others, and some not at all. My efforts are centered around feeling the whole thing at the same time (one thing moves everything moves?). Sometimes I feel something like a band running around the shoulder joint, more or less vertically, but I'm not sure if that's because I'm using too much latisimus dorsi or trapezius or whatever it is I'm using.
As usual, the more I write the less confident I feel. Like I said, i don't practice enough...and I probably shouldn't try to chime in because of it, but FWIW, there's a start. I might get ballsy and shoot a video of what I look like. I'll try to think more about it and see if I can't find a better description...might help to practice more too...have I mentioned I don't practice enough?
What do you tend to focus on?
p.s. in my defense I'm juggling my 2-year old, my 5-day old and this post, so I apologize for any haphazard descriptions.
Take care,
Matt