As a dancer, if I'm at the end of a line and see that there are particularly lost-looking newbies in my foursome who are about to be "spat out" after the walkthrough, I'll sometimes rotate our foursome to make the new folks progress into the set so that they won't have to deal with turnaround confusion right away. If I don't find out until after the walkthrough is finished that it's a right-progressing Becket after all, then in my attempt to help I may have actually made it worse for them.
So as a caller, I think it's always helpful to give people a heads up - either "line up Becket; this dance will progress to the right," or (my preference) "line up, take hands four, then turn one place to the right into Becket formation." It's true that a lot of dancers don't notice or care, but I think enough of us do care that it's worth giving just a word or two to those who are listening for it.
As for identifying shadows, I find that unless I have *really* clear notes, if I try to identify the relevant shadow at the beginning of the walkthrough it often backfires on me. I usually prefer to just walk everyone through the dance until they actually get to the shadow part, and then tell them "remember this person."
Koren Wake
dancer, caller, musician
Seattle WA