I just hope that this time around they don't spoil so much with trailers and merch. Can you imagine if nobody had seen the double-sided lightsaber until Maul bust that puppy out in the Naboo duel? You'd have had the audience going nuts. As it was, it was spoiled for pretty much everyone in the trailer.
A good comparison might be for Episode VII that they should never show Luke in the trailers. Maybe just him hooded and obscured, or his voice saying, "The Force will be with you... always" or "Leia, hear me..." In fact, they should do two different initial trailers, one focusing on the original cast and the other on the new cast, with Luke being the common thread (assuming the search for him is the plotline, as we are guessing).