On arrival at the airport fill in the arrival card, make sure your passport carries the arrival stamp and, before leaving customs area, exchange currency and keep the receipt to reconvert unspent rupees to your original currency. Carts for luggage are free: do not pay anyone, not even a tip.
Indian customs have a Red and a Green Channel. Use the Green one only if you are sure you do not carry any goods that are dutiable in India. If you carry a dutiable item like a camera and will be taking it back, inform the customs officer and have them make a suitable entry in your passport.
Check baggage for damages before you leave the counter. File a claim immediately and obtain a report too before leaving the airport.
Taxis and local transportation outside the airport may rip you off. It is best to choose a prepaid taxi service. Ask fellow travelers the local fare and pay only that amount. This applies to local transportation too anywhere in India. Book into only standard hotels. Be careful to ascertain rates first at any hotel. Foreigners are considered "soft" targets by taxi drivers and even shopkeepers.
English is widely spoken and understood in India and if you know English it helps.
If you travel by train or by air, make sure to book in advance. Seats on important and busy routes are always booked. Contact approved and reliable travel agents.
Explore India on your own or choose a reliable tour operator who not only arranges visits to important cities and places of interest but also takes care of accommodation and meals.
Carry packaged drinking water for hygienic reasons. Tap water may cause stomach upsets.
Carry antibiotics and remedies for fever, stomach upsets, flu and common infections.
Banks operate between 10 AM to 3 PM throughout India so if it currency or exchange matters you want to deal with, visit the banks between these hours.
Large and reputed establishments will accept International Credit Cards.
When visiting temples and mosques, always make it a point to leave footwear outside.
Keep all important travel documents with you, safely and never entrust them to anyone. Also make copies and keep them separately. Keep them and credit cards and cash in an inside pocket, safe and secure.
Tips: Do not tip taxi drivers and autorickshaw drivers. At restaurants, a 10% tip will work fine.
While shopping at roadside markets and stalls, be careful: they always ask an astronomical price of foreigners. You can bargain, it is the way of life.
Do not leave any of your belongings unattended in any public place.
Be careful whilst in crowds, there may be pickpockets around.
As anywhere else in the world, you will come across hustlers who offer a good deal on an antique or some wonderful item. Be careful.