Food stalls/snacks in Tokyo?

Hi guys, I'm going to Japan in a couple weeks for the first time. I want to know where are the places I can buy snacks in Tokyo? I'm talking about, for example, mitarashi dango. Can I only buy it in supermarkets? Also, taiyaki. Thanks!

Yes, you can buy them at konbini or supermarket.
Konbini: http://www.youtube.com/watch?v=w60UH5hgsgM&t=14s
SuperMarket: http://www.youtube.com/watch?v=QYHzyLrtvBY

But of course, more delicious one sold at specialist shops called Kanmi-dokoro or Wagashi-ya.

I can recommend to visit Asakusa or Sky-Tree.
Maybe easier to understand than other places.
http://www.youtube.com/watch?v=V7cM3jvX6fk&t=4s
http://www.youtube.com/watch?v=Q4WJR_nlVc4

"Taiyaki Time" is under Tokyo Sky-Tree.
MAP: http://goo.gl/maps/pJ4n3
http://www.obn.co.jp/taimu/menu/

"mochiya Riichi" is at 2F in Tokyo Sky-Tree.
They serve rice-candies such as mitarashi-dango.

Aha! I was looking at pictures of Asakusa shopping streets earlier and thought, "They MUST sell those skewered dango there, it totally looks like the place!" I'm just silly like that, I want to buy it from one of those shopping streets rather than in supermarket or convenience store. Thanks a lot!! I may or may not get to go to Tokyo Sky Tree, but I'll try. My one-week stay is very packed. Anyway, thanks again.

Two of Tokyo's most famous taiyaki are in Ningyocho and Azabu-Juban. Both listed here:

http://foodsaketokyo.wordpress.com/2010/04/09/tokyos-shoutengai-shoppi...東京の商店街/

Both are good. Usually a line at the Ningyocho shop.