These quick travel tips will help you to avoid being harassed and ripped off in India.
Always reserve a room in a hotel before you arrive, especially in major cities such as Delhi and Mumbai.
As a general rule, ignore anyone who approaches you unsolicited, no matter how genuine they seem. Most often they'll want to take advantage of you in some way, or take you to a place of their choice so that they get commission. Often they'll offer their friendship first, which sometimes includes an invitation for a meal with their family, to gain your trust. However, more often than not there will be an agenda behind it.
Never tell anyone that it's your first time visiting India. They'll immediately view you as an easy and naive target.
Unfortunately, politely smiling and saying "no thank you" will not stop you from being harassed. Instead your good manners will often be viewed as a sign of weakness. You'll find that if you hold your hand up with the palm facing towards people, shake your head and look away, they'll be more inclined to leave you alone. It can also be useful to raise your voice and sternly tell them "NO".
Don't be afraid to make a scene, especially if you're a woman. Indian men have difficulty dealing with extremely displays of emotion, especially from foreigners.
Make sure that you always negotiate a price before any services are performed, otherwise you may be asked to pay an inflated price at the end. For example, you encounter a holy man at a religious site who offers to give you a special blessing. After the blessing has been performed, he requests an exorbitant amount from you, which could be 1000 rupees or more, saying that this is his fee. Never feel obliged to pay such an amount in any situation like this. Only give what you feel is reasonable. This applies anywhere someone asks that you pay a high price for something.