After a good friend asked me where do I get the ingredients I use, I realised may be I should explain a bit more and even give brands wherever possible. Also I will try to explain why I use those ingredients.
Margarine: Margarine I use instead of butter for many reasons. It's always better to use plant based products and margarine is one of them. Margarine may not be healthy but it's much more healthier than using butter. Margarine is cholesterol free and anyday better than having butter that's 'fortified' with pesticides, hormones, antibiotics and god knows what.
I use margarine that is available at my local grocery. Generally it comes under a brand called Rajvi or from a local dairy. Whatever I use, I always check the ingredients or call the company if I have any doubts. They are happy to answer your questions believe it or not.
Tofu: Also called Soya Paneer, it is coagulated soy milk and made just as paneer is made but without the use of animal ingredients. Tofu is usually made Firm, Medium or Silken but the Indian brand of tofu is available firm and in two flavours one plain and one spicy. This is available any grocery store or super market. There is also a Japanese import available which is much more expensive but availabe in the three consistencies. If you don't find something always ask the grocer or the store in-charge. They generally know where you can get it or will order it for you if you are lucky.
Soy Milk: Available at all grocery stores and super markets now. Always check the flavour of the soy milk you are buying. I use Staetta because it is free of preservatives but you could use the other local brands. There is a brand that is imported from the U.S. but it is way more expensive.
Oils: While baking I either use oil or margarine. It's important to use non smelly oils like rice bran oil, sunflower oil, safflower oil. Also if the oils are organic and cold pressed it's much more better. Cold pressed oils are available at shops that only deal in oil. In Mumbai, for instance it is available in Crawford Market. Why cold pressed? When oil is made by the usual refining process it is heated. When we buy it and use it, we again heat it and this heating releases carcinogens that we can avoid when we use cold pressed oils.
So that's mostly what basic baking requires and you'll see you don't really have to go out of your way or your choices are not limited if you try cooking vegan.