I think that 343 should make some very low key advertisements that will be hard to notice, for example, I think they should make a random youtube account with some generic name and upload some normal youtube videos to it, and then put a short halo 4 concept art photo on it. Or they should just put up a poster somewhere random of a halo 4 picture with only a little information. I think that this would be a cool way to advertise the game.
To be honest i think 343i are going to be big with Advertising Halo 4
>:3
I expect big advertisements, but I think they should do some small advertisements in between.
Lets just hope they start showing SOMETHING soon. Im tired of waiting when they could be giving us ANYTHING, I dont care what it is as long as it has to do with Halo 4.
Hmm. Who knows!!! 
SUPERBOWL commercial
They will probably do really small advertising, to rise suspicions and hype, then go in with a bang.