This topic was mentioned on a recent seminar I attended, the gist of what was said was something like;
- Watch the feet first for the ashi sabaki
- Then watch the relationship between the two centres, how tori moves their body as a whole in accordance with ukes movement. (tai sabaki)
- Then come the hands, (te sabaki)
- and if you're lucky enough to get another repetition of the technique, try not to focus on any one specific thing, but get a feel for how everything fits together, or at least how to co-ordinate the first three points.
Then all you've got to do is remember it and not get confused with something you've done before.
Or think that what was just shown is something that you already know...