Releasing extensive, non-spoiling demos/trailers in a timely manner wouldn't hurt, either. Konami hit the nail right on the head with their "surprise" MGS2 teasers in past E3s, following that up with the famous public (ZOE) demo. Capcom and Namco did the smart thing by including VJ and SCII in last year's GC Demo Disc (tho unfortunately, that's the only significant "take-home" demo we've ever got to date). Releasing the super-sized, meaty Resident Evil 4 trailer in Famitsu Wave DVD well in-advance of the game's release was another good move, though they (these 'subtle' promotions of Nintendo titles) pale in comparison to the long-term benefits of PS2/Xbox's periodic demo/preview disc programs, which have been great sources of media that can possibly make a more effective/definitive impression on the viewer than simply visiting an internet site and downloading a tiny video clip.
Long have I wished for Nintendo to make significant improvements in this regard. Sure, I do see things improving, but it's all been at too slow a rate, which is why I think the scene is still relatively quiet, with many titles still not getting proper retail attention.
Then I continue to wonder why GBA advertising historically seems more exciting/interesting than GCN advertising.