India has no single cuisine. The subcontinent's regional cooking traditions are so distinct that "Indian food" as a concept tells you almost nothing — it's like saying "European food."
The North
The cooking of Delhi, Rajasthan, and Uttar Pradesh is what most people outside India know as Indian food: tandoor-cooked breads and meats, rich curries, and dishes like butter chicken, dal makhani, and biryani. Street food in Delhi is exceptional — the chaat (savory snacks) culture is a world of its own, with variants like golgappa (crisp shells filled with spiced water), aloo tikki (potato cakes with chutneys), and papri chaat (crispy wafers with chickpeas and yogurt).
Punjab produces some of the most satisfying food in the country. Amritsari kulcha, sarson da saag with makki di roti, and the region's bold use of dairy make Punjabi cooking deeply comforting.
The South
South Indian food is generally lighter and more vegetable-forward than northern cooking, though seafood is central on the coasts. The dosa — a thin fermented crepe made from rice and lentil batter, served with sambar and chutneys — is one of India's great dishes and available across the country, but it reaches its finest form in Tamil Nadu and Karnataka. Idli (steamed rice cakes), vada (savory doughnuts), and uttapam (thick pancakes) are the other cornerstones of the South Indian breakfast, which is one of the best meals you'll eat.
Kerala cooking is famous for its use of coconut milk, fish, and seafood. A Kerala fish curry is entirely different from a North Indian fish curry — subtle, aromatic, and often served with rice. The Sadhya, a multi-course vegetarian feast served on a banana leaf at festivals and weddings, contains some twenty dishes and is an experience rather than just a meal.
Hyderabad is the home of Hyderabadi biryani — arguably India's finest biryani, made with basmati rice, spiced meat (usually mutton or chicken), and slow-cooked in a sealed pot. Worth going out of your way for.
Vegetarian India
India is one of the best countries on earth to be a vegetarian. The diversity of plant-based cooking is extraordinary, and dedicated vegetarian restaurants are everywhere. Many communities — Jains, many Brahmin Hindus, Vaishnavas — have developed elaborate vegetarian traditions over centuries.
Street Food
Street food is a constant pleasure and perfectly safe if you apply common sense: eat at busy stalls with high turnover, avoid anything that has been sitting out, and let your stomach adjust in the first few days before diving into the full range.
Drink
The tea — chai — is ubiquitous: milky, sweet, spiced, and served in small glasses everywhere. It is usually excellent. Filter coffee in South India is a completely different drink: brewed with chicory and served in a metal tumbler, it is one of the small joys of traveling in Tamil Nadu and Karnataka.
Kingfisher lager is the most widely available beer. Local rum and whisky are cheap and variable. Feni — a Goan spirit distilled from cashew apple — is worth trying if you're in Goa.