I think one of the biggest things is how you land into your lockoff, and how your body is positioned. If you’re not comfortable, in good form, and relaxed, you won’t be able to be really still in a locked off shot. I try to be aware of my approach into a lockoff, so that I’m preparing to land solidly in a comfortable place, with the rig close beside me, and my weight solidly on one foot (so that I’ll be able to adjust quickly and without weight transfer if needed). If you land in an awkward position – mid-step, mid weight transfer, rig way out in front of you or on the wrong side – it’ll be hard to physically hold that weight. Another thing is that I very rarely kiss off moves at all. Kissing off the rig means that you have to do a lot more mental work as you’re getting into a stop or starting up, and it means the rig can be farther out in front of you, or in an awkward position. I know it’s taught at all of the workshops (and it is a good technique for learning to separate your body from the rig), but my experience has been that you can get cleaner starts and stops without kissing off. My logic is that I’d always rather use more mass to accelerate and decelerate, to smooth out those movements. By tying the rig’s acceleration to my body’s acceleration, I can achieve more solid starts and stops, and it becomes easier to land in a comfortable position.

Here’s another thing to consider – in a lockoff, your instincts may tend to push you towards micromanaging the frame. Since you no longer are occupying large parts of your attention with moving or blocking, you will tend to over-focus on the frame, and constantly “chase” perfectly still frame edges. (Which in fact results in the opposite!) I find that I need to consciously slow down my thought process, and remind myself that the camera is fine. Larry McConkey taught me his technique for long lockoffs, which is to acknowledge that the frame is solid, and mentally “zone out”, just listening to the dialogue. Periodically, bring your attention back to the frame, and check that it’s still good. There will almost certainly be a little subconscious twitch of your hand when you do that, but you can hopefully time it so those check-ins are at inconspicuous moments. Then, a few lines before you will need to move again, you can focus back in, so you’re not late to move again. I’ve even had for a particularly long pause my dolly grip tap me on the side to let me know that we’re going to pick back up soon, in case I get lost in the dialogue. This technique does rely on you not having to make any adjustments during the lockoff, however, so it’s only useful if you’re doing a more architecturally based frame, or something like people sitting down where you know they won’t shift or move. 

Hopefully that will help. I think you’ll see the biggest improvement by getting more comfortable with your body and how you land.