Delhi is served by Indira Gandhi International Airport (IGI), one of the busiest in South Asia. Terminal 3 handles most international and domestic flights; Terminal 1 handles some budget domestic carriers. The Airport Express Metro line connects Terminal 3 to New Delhi Railway Station in about 20 minutes — it is clean, fast, and cheap, and the obvious choice unless you have a great deal of luggage.
Delhi has two major railway stations: New Delhi Railway Station near Connaught Place and Hazrat Nizamuddin in the south, which serves trains to Agra and Rajasthan. Most through trains from Mumbai, Kolkata, and Chennai arrive at New Delhi or Old Delhi Station. Book train tickets well in advance on the IRCTC website — popular routes sell out weeks ahead.
Long-distance buses from Jaipur, Agra, Chandigarh, and other northern cities arrive at the Inter-State Bus Terminal (ISBT) at Kashmere Gate, connected to the Metro. From Agra, the Gatimaan Express (90 minutes) and the Shatabdi Express (2 hours) are the fastest and most comfortable options.