Security You have to plan ahead and be wise. It's not that Indians are so dishonest, but dishonest people know there is money to be made from tourists so you'll meet more then your share of people who will try and cheat or rob you.
Taxi and rickshaw drivers often overcharge or insist on taking you to places they want you to go, not where you want. Know what hotel, shop etc. you want to go to and insist. Be firm and try and be polite, if that doesn't work insist loudly. Check your bills in restaurants and hotels to make sure it's correct. Have waiters open the bottle and pour your drink out in front of you. Some travellers have been given knock out drinks and lost everything.
Sadly the police are often corrupt. Tourists I've heard of were charged thousands of ruppees for a meal rather then hundreds and when they called the police the police sided with the crooked waiter rather then the tourists. Police have searched rooms in guest houses for drugs and then the next day that room has been robbed of valuables like a camera, a disc-man etc. (because the police contact the robbers and get a cut)
Guard
your things. Get travelers cheques, use a concealed money belt,
have a sturdy chain and some little padlocks. You'll need to
chain and lock your luggage to the seat of the train (even
Indians do that), lock your things in your room and if possible
double lock your door. Double lock while you are out and also
while you are in, some robbers use knock out gas and rob the
people while they are sleeping. The biggest hassle and rip off
comes from renting motorcycles or scooters. Click this photo.