Indian food in the US, and in India:
If this belong in the India category, please move it, mods.
I'm going on a trip to India in September with girlfriends, and while I do like the few Indian I have tried, and am not afraid of spicy and hot, I don't have a broad knowledge of the cuisine.
We'll visit Delhi, Agra, Jaipur, Mumbai and Goa.
If anyone can pass on a recipe or website or cookbook or anything I should try to learn more, that would be great! Or recommend a dish I should try in a restaurant.
Before I travel I like to have a good base knowledge of the cuisine.
If I may, I would like to recommend that you go about getting to know Indian food in a different way. You see, the local cuisines in each of these cities are nothing like each other. There is so much that you can eat in India that you really don't see in the US on menus, unless your locale has a large South Asian community with a "Little India" type neighborhood. You could try looking at some cookbooks which focus on the regionality of Indian cuisine.
There will be some types of restos that serves pan-Indian favorites like Punjabi-Mughlai restos, breakfast or deep fried snack item places (transport me to a great kachori stand!!! Parathas! Chhola bhatoora! Halva puri! Look up this stuff if you don't know what it is and seek it out!), chaat places (but trust me, the popular chaat in Delhi is very different from the popular chaat in Mumbai), South Indian dosa places, and Indian Chinese restos. But there will also be a lot of local specialties in each place, or well loved and famous restos or food stalls (well known ones which are reputedly hygienic) in each place that are must-tries. Barring Agra, all of these places have vibrant eating-out cultures which will be accessible to you with the right guidance. (I haven't been to Agra in like 15 years and was only there briefly to see the Taj Mahal, so maybe someone can correct me if I am wrong, but I don't believe that Agra has any notable resto culture in the same way these other places do, and most visitors (foreign tourists especially) just eat in the hotels that cater to Taj Mahal tourists, and these hotels serve Mughlai and continental type stuff. Goa's resto culture also caters to tourists (both Indian and foreign) but it is more diverse and there are cool places to get really good seafood, Goan cuisine, other types of Konkani cuisine, plus fun dosa places.)
If you are a die-hard foodie bent on eating a great meal of local cuisines and well loved restos in each place, I recommend posting on the CH India regional board about each city separately, asking on Indiamike.com, and asking what are some must-eats in each place and asking about the local food culture (cities like Delhi and Mumbai have vast offerings of all sorts from all corners of India, also), and also looking at youtube, like at Rocky and Mayur's show for each city (they are in short segments) or other India food travel shows for inspiration, and create a check list of places to try to hit. There are also Delhi and Mumbai food bloggers with great posts to check out. (Finely Chopped based out of Mumbai is a good one!) Foreigners who don't know where to eat will complain about tummy upsets and gross food in India. But India is foodie paradise if you know where to go in each city. I think by having a check-list and doing some research on what specifically to eat in each recommended place, you will get to know the diversity of Indian food by eating in each city.
I can give you some recs.
For Delhi, but it's huge with lots of traffic there, so you may want to ask on the CH Indian board and in the Indiamike forum Delhi section for where specifically you will be staying or near to sites you will be touring, also.
Some must eats are Karim's for classic Delhi Muslim food. It will be oily and spicy real-deal stuff. Also, have a fancy meal at renowned upscale Mughlai-Punjabi resto Bukhara---you *must* try their famous smoky daal. Also, you must go to eat in Paraathe wali galli (paraatha street) but I don't know where to tell you to go, but ask here and on Indiamike's Delhi forum for some names, like try small plates of a variety of things and then finish with some heavy and delicious paraathas. Also, I love this restaurant called Saravana Bhavan, they have a couple of branches in Delhi. They are an amazing Chennai style Tamil restaurant...this is actually one of my favoritest restaurants in the whole world, and it is a good opportunity to try very well made dosas and other South Indian "fast foods."
Also a favorite resto of mine in Mumbai is called Rajdhani and they have authentic pure veg Gujarati and Rajasthani thaali. Even though you will be coming from/going to Jaipur in Rajasthan, I am still making this rec because I really enjoyed this place so much. If you don't know what thaali is, you should look into that. I'm sure you will get plenty of good recs, as Mumbai is an awesome foodie city, but that is mine. Some classic Mumbai items to ask about: where to eat great pao bhaaji and vada pao (this will be a heavy snack or a lunch.) Also, get a rec for a good Maharashtrian restaurant...Mumbai is very multicultural and multiethnic, but Maharashtrian food is indigenous there, so see if you can find a good place to try one (you will actually find restos specializing in specific regional cuisines of Maharashtra like Kolhapuri, etc...but that may be too much detail for you...just find a good Maharashtrian resto.)
You are going to Jaipur and there are surely several renowned places to get Rajasthaani thaali there, be sure to try this item called daal-baati, it is Rajasthani daal served with hard baked whole wheat flour balls that you break up into the daal. This was traditionally desert food since you can make the balls without a lot of water and bake them outdoors. They also make a dessert by grinding up the baatis with ghee and sugar, called churma. You should ask on the boards/forums where to try this in Jaipur. Also, try to go to a Gujarati farsaan (small snacks) restaurant in Jaipur and order multiple plates of chaats and farsaans, some names to keep in mind are dhokla, khaandvi, and haandvo. Sorry, I cannot give you any names of places to go. For items like dhokla and khaandvi, this is preferred to be eaten fresh as can be, so places that sell these items sometimes run out in the late morning, so maybe go for this as an early lunch/late breakfast. I was only in Jaipur twice and a very long time ago, so I cannot give you specific recs...but I just wanted to give you some items to have in mind to look for. It may also interest you to try a "Jain hotel" which is a restaurant that serves food that is made according to Jain dietary standards with no onions and garlic (pure veg). These are all over Mumbai and Delhi, too, but it might be fun to try one in Jaipur.