These are based on my experience over many years of cooking in India and the U.S.  Happy cooking, and may all your dishes be awesome!

Ginger-Garlic paste (homemade)
In my house, as in many others, we always make a ginger-garlic paste and store it for up to 2-3 weeks in the fridge or longer in the freezer.  You can grind it in a large mortar and pestle, use a wet-dry grinder or, as I do, chop it finely in a food processor.

½ cup ginger, peeled and chopped roughly
½ cup garlic, peeled and chopped roughly
½ teaspoon salt (it acts like a preservative)

Combine and food process till fine.  Pack into a small glass jar and cover with 1 teaspoon of oil.

(3 large cloves of garlic) + (1 inch x 1 inch cube ginger) = 2 tablespoons of ginger-garlic paste

Ginger or Garlic paste (commercial)
You can always buy ready-made pastes, although the homemade version is much better.

3 large cloves of garlic = 1 tablespoon of finely chopped garlic
1 inch x 1 inch cube ginger = 1 tablespoon finely chopped ginger

As a general practice I always cook with red onions, perhaps because in India that’s what we use and I prefer their sweetness.  But you can use either red or yellow in these recipes.  Also, to save time, I tend to use the food processor in pulse mode to chop my onions, unless the recipe calls for fine slices.

1 small onion = ½ cup finely chopped
1 medium onion = ¾ cup finely chopped
1 large onion = 1 cup finely chopped

In all my recipes I have asked for the use of whole peeled canned tomatoes.  They are good quality and work really well for Indian curry bases.  I do not like using crushed, pureed or chopped tomatoes – they are never as good as whole and can totally throw the recipe off.  If the recipe calls for crushed tomatoes it is simple to break up the tomatoes with your hands or fist or to chop with a knife.

In the summer when the tomatoes are in season I sometimes use fresh plum tomatoes but I always peel them first.  Also if using fresh tomatoes use 1½ times what the recipe calls for.  There are two ways to peel:

  1. I peel raw tomatoes with what I call my magic tomato peeler – it is slightly serrated and works like a charm. The brand I use is a Messermeister but I am sure there are other brands that work just as well.

  2. Boil a large pot of water. While water is boiling use your paring knife to cut out the stem. Then slice a shallow X in the bottom (blossom) end. Once the water has come to a rolling boil add the tomatoes for a few seconds. Using a slotted spoon take out the tomatoes. The skin will easily peel off.

I NEVER use canned tomato sauce, crushed tomatoes or tomato paste.  
Here is a good article on tomatoes.

1 medium size tomato = 1/3 cup chopped

I really struggled with salt when I first came to this country.  The salt in India is way saltier than the salt here, and I could never get myself to add adequate salt in my dishes and was constantly making my husband and friends taste for salt.  When a friend suggested I should write the quantity of salt in my recipes I thought that was a brilliant idea.  I have used regular table salt for my recipes.  All fancy salts lose their unique flavor during cooking so I find them a waste.  But after cooking if I feel the dish needs more salt I always use fresh ground sea salt from my battery-operated salt grinder that I absolutely love!

Ghee and Oil
When cooking Indian food it is very important that the oil be very hot before adding the whole spices.  A good visual clue that it is hot enough is when the oil changes from a perfectly smooth surface to a shimmering surface.

In my house in Calcutta, where I grew up, all our food was cooked in ghee (clarified butter).  Even potato fries were made in ghee!  Well, things have changed and now 99% of the cooking in India is done in vegetable (peanut or mustard) oil, though for certain dishes such as dal (lentils), the tempering is still done in ghee.  Feel free to use an oil-ghee combination when you want to.  Our everyday food is far from being rich in ghee or heavy to eat.  I feel the challenge is to make food tasty using as little oil as possible, and that is what I do in my cooking practice and for these recipes.

I use Grapeseed oil for my cooking.  Ghee is fantastic and a must for tempering dals.  There is a lot of controversy about which oil is good for cooking and high heat cooking.  When I get to the bottom of it I will post it here but for now, use ghee and any oil that can handle some heat and does not have a very strong flavor of its own.  In South India they tend to use a lot of coconut oil, and while I love the taste I also know that for health reasons it should be used judiciously.

Dry red chili: Many Indian dishes use whole dried red chili peppers.  They are not intended to be eaten but used to add a unique flavor to the oil. If you want a spicier dish, you can squeeze out the sauce and seeds from the shell and mix it with the curry.

Fresh green chili: As a rule of thumb, the smaller the green chili the more potent it is. In Indian stores in New York you can get a small fresh green chili that is really potent, and that is what I use primarily in my cooking.  You can also get it in Asian grocery stores as "Thai chili". You also get a longer chili, which has a great flavor but is not as potent. Serrano chilli is the closest substitute, but Jalapenos can also be used, though use less of it (about half) as they are larger in size. See the chart below to compare the spiciness of these chilies.

De-seeding the chilies makes them milder.  I sometimes de-seed and sometimes don’t, it depends on your spice tolerance.  But you must wash your hands well after doing so and don’t touch your eyes right after!

Chili spice chart (spiciest to mildest):
1. Thai green chili
2. Indian green chili
3. Serrano green chili
4. Jalapeno green chili
5. Indian long green chili
6. Anaheim green chili

Cilantro (fresh Coriander leaves)
I was staying with a friend in Rome a few years ago and offered to cook a nice Indian meal for her family. Much to my surprise, fresh cilantro was available only in one store in the center of Rome. I thanked God I lived in the U.S. where cilantro is as easily available as fresh parsley!

But I also have friends who don’t like cilantro, and for them I keep some of the dish aside before adding the cilantro.  If you don’t like it, don’t add it--it’s totally fine. But please don’t substitute parsley for it.  That will greatly annoy the God of Spicy Things.

I normally wash my cilantro in cold water and spin dry it before chopping it.