In that one scene when he gets flowers for Charlie, he freezes time and walks over to the flower shop?
I guess he can freeze time for more than one minute (<--taken from his blog), after all.
He theoretically could teleport if he knows where the flower shop is. But not without freezing time, as well. Ok.
I suppose he left some money on the counter and didn't just take the flowers. No, he wouldn't do that.

Somewhere in between he serves a table. The people don't wonder where the food was coming from all of a sudden?
It's the same as with Mohinder on the train, I'm sure.

In the origami scene he certainly needed much more than a minute to fold and stuff the room with all those birds. He's leveling up, I guess. I suspect he will be pretty good with the freezing now that he returned. So good that he doesn't need to do that darned time travel again, I hope.

And then the kiss scene...many people wonder how and why Hiro got taken back to Japan right then.
I think his power works like this:
1. first he needs either a visual or the knowledge of the place in his mind, to form a picture in his head (NYC poster, Charlie's picture before)
2. then he needs to concentrate a little

Ok, we got the visual. Hiro was thinking about Charlie and himself being in Japan. They were talking about it right at that moment. I'm sure he had it on his mind.
When they are about to kiss, Hiro needs to focus...he doesn't want to ruin this moment, especially after what Charlie has just told him. But he's still thinking about Japan and more specifically a place he knows, like Tokyo on the roof of his company.
Ok, he could have picked a nicer spot to think of, I don't know.

When he both concentrates with a location on his mind, that's I think is what enables him to teleport. Unfortunately, this combination happens right then and he jumps back to present day Tokyo.

From there he has no choice but to take normal means of transportation or he would end up who-knows-when in the diner. He could go there, because he has been there before. But he knows he might miss the whole "save the cheerleader, save the world" stuff and he's still responsible enough to not risk that to happen. Too bad it's already done.

I think it's evident that he increased his time freezing a great deal while back in the past. Helps with putting some bigger obstacles in his path in the upcoming episodes, I guess.

Edit: In another thread I said this is not mine idea. I should do the same here. Someone already came up with the teleport idea back when Hiro first teleported in the pilot. We just got more proof in the meantime. What threw me off was that Hiro didn't really look at the poster of Times Square, he stared into the camera and the poster was to the right of him. I guess he had seen it though and was just thinking about the image.

Yup, that about sums it all up I think.

i like this theory..that explains how he was able to time travel the first time when he was on the subway, he saw the poster of times sqaure..and just kind of spaced out, probably "thinking/concentrating" on times sqaure, causing him to teleport there

"I need you to tell me where we meet."
He said that on the train , didn't he?