mgoetze, on 2013-January-04, 12:51, said:
I feel confident in telling even beginners that this [cue bid] should show an invitational or better hand with a spade fit.
It is probably worth telling inexperienced players that this is OK if the change of suit is forcing; if the change of suit is merely constructive, then the cue bid has to do a bit more heavy lifting, and can't be restricted to hands with a fit.