Stay Healthy: Always carry a water bottle with you. Either boil your own water, or make sure to buy bottled water from a reliable distributor (Bisleri, Yes!, etc.). If you eat on the street, consume only fresh fruit or food that is boiled or fried. Food that hasn’t been cooked at high temperatures could make you sick also. So be prepared in advance.
Be Safe: Always keep your passport and other documents papers close to you. Don't leave your important documents in your luggage. Also keep 2 passport size photographs in a safe place. You can find beggars on streets in India but don't give them money, it's better to buy a meal and give them.
Transportation: Remember India is the second most populous country in the world. If you want to travel by bus to local Bazaars (markets) u can't get a seat easily; buses are fully crowded. Better to arrange your own personal Auto-rikshaw. Transportation is cheap in India.