Haven't played it.But basically you just have to knock people into specific spots.You can do this by holding x or b and back and you perform a launch type of attack,Or you can perform a combo that ends with that type of attack.I'm not entirely sure if everyone will have one.Hope that helps.

THX Dude...
Do you know if your meter gets depleted?
How do you know where you have to stand?
I've seen Grundy doing a combo that ends with it, Superman too...

Well in one of the interviews (I think someone posted it on here) I think they said it was forward and x (playstation) when your in the right are and I don't think it takes your bar off. Icould be completely wrong though

Can you finish a character with a stage transition?

Sure. The opponent loses A LOT of health during a stage transition. Anyways: I've watched all videos and trailers COUNTLESS times and I think I've figured out how a stage transition works exactly:

The input is backward + A (Xbox360) and backward + X (Playstation 3). In some matches you can often hear someone (from NRS) say "press backward + A" and tadaaa! Stage transition (it was also confirmed by Hector Sanchez that A and X will be used for stage transitions). It could also be that you can press backward as well as forward for the transition (similar to throws). Hmmm.... I've hoped that they used the Giimmick button for the stage transition instead of A and X. Otherwise, it is possible to do that slow move by accident (in a combo for example). For the time being, a stage transition as such does not cost any power meter, perhaps because the transition move comes out veeeeery slooooooowly. It's probably very hard to hit a skilled player with a transition move and cause a stage transition. However, if you use the transition move in a chain combo it'll cost 2 meter (you can see that in demos).
As one of the users already said, a stage transition can only be performed at certain points in the stage (for example at the corner). There are no indications of where those points are, you just have to find out by yourself. If the transition move is performed outside of that specific spot, however, it causes a wall bounce instead, i.e. the opponent is catapulted against the corner, bouces back and is free for combos / juggles (watch the SDCC Trailer. It's everywhere). It's quite clever, as your meter is not depleted for nothing.

I guess that the transition move is blockable. It would be stupid if it is not.

I think that's about it. Do you have any other questions?

Wow.. awesome answer dude :P

THX a lot. Yeah you're right, within a combo it costs meter, without combo not.
At the beginning you say input is backwards+A but then the NRS dude says backwards+B?

In the metropolis city stage batman slams grundy from the roof to the ground...It was kind of a different combo that ends with a ground slam...

Sorry, the "backwards+B" was a typo XD I've edited it.

Yeah, I also thought about the rooftop stage transition. I have no idea how that works, but it seems that this stage transition is activated by certain special moves (probably enhanced specials). You can also see Batman didn't lose any meter, which is interesting because a couple of moments later the same combo was performed again and Batman loses one meter due to an enhanced special. Still, I dunno what to think about that. This transition costs almost no meter, does A LOT of damage and is really easy to perform...