I think I'm getting a little tired of all the new radio signals that take us to places. Why can't an NPC or a note or maybe even ED-E be a way to announce a DLC.

Its how they did it it FO3 with all the DLCs, I know its easy to implement but add a little pizazz.
Use NPCs like the Forecastor to tell you of how hes thinking thoughts and his thinking turns him in a certain direction that the forecastor encourages the Courier to go.

Or you get a recording or broadcast from ED-E or another eyebot that leads to the Big Empty. You know stuff like that. (Oh wait ED-E can be killed! forget this)

Also hope they'll make use with all the raillines the NCR use or a raft in the Colorado to reach the DLC/Expansion area.

Ideas?

You could get a message saying that there are rumors going around that the canyon wreckage has been cleared or something along those lines. Best I've got and it isn't much xD

They did a nice job with Point Lookout, spreading the leaflet about the Duchess Gambit and selling Point Lookout's Punga fruits in the Capital Wasteland.

If DLC directions were more subtle than this, the forums would be flooded with "OMG WEAR IS MAI DLC!!!!!!"

The radio signals are probably the way to go when a DLC is released; it shouldn't be a chore for the player to find the new content he just purchased. But it's really annoying on later playthroughs.
What I'd like is for the GOTY to implement the DLCs a bit more organically into the main game. Point Lookout did it okay and Broken Steel was seamless, but the radio signals for the others could have been better implemented in the combined version. Mothership Zeta could have had an observer warning players that people who approach the crashed ship are drawn into the sky (or a simple pop-up Dead Money style); Operation: Anchorage could have come to our attention through conversation with the outcasts and a runner hired by Werther could approach us about the Pitt.
Maybe in the GOTY version of NV, around level 15 we can start getting random conversation options about a radio signal near Camp Forlorn Hope, or perhaps there is a desertion problem we are asked to investigate; we'd discover the common link is a radio signal.
Anyway, I agree with the OP that the DLC hooks are pretty unimaginative, but they sort of have to be that way at first. Later, I'd like to see them woven into the game more subtly.

What about someone running up to you asking for help, through the dialogue you will get the new quest and directions of how to go there.
If you killed this person then you still get the quest and the objective says "Loot the man and see if you can find out what was so damn important."
Doing that you get a note and can still get to the quest.

But yeah, no more damn radio signals, it's just flat out lazy design to attract us to the DLC.

No rumours either. When you install the DLC halfway through a playthrough it kind of makes sense that you heard some 'rumours'.

But on new playthroughs it seems kind of stupid. Where the hell did you hear the rumours?

I'd like a DLC to start with mob of people trying to kill you and you have to try to find out why. Yeah it's a bit Hollywood cliche, but I wouldn't mind seeing that in FONV. =p