don't
Do not pay the kids begging in Hampi. Most of them are not that poor. They fake poverty to make extra money. To the kids selling stuffs, pay a reasonable price for the merchandise but nothing extra as a gesture of kindness. Your kindness in form of a little extra ruins the kids' future.
If you are staying at Virupapur Gadde side of the river, plan and return by 6'o clock. If you have a train/bus to catch in the night, checking out before 6'o clock in the evening helps. If the ferry closes, the auto/car option becomes a much longer and costlier affair.
respect
Out of deference to the sacred nature of the site, do not consume drugs and alcohol in the area.
When visiting the temple or ruins of former temples, cover up and do not show too much skin. The locals will not stop you, but may bear a silent grudge. Be a good guest.
Please visit any monument only for the sake of visiting, but not for any other purpose. Please do not scribble or climb or sit on any monuments... please remember that they have stood rain and sun for centuries and have to stand for next many centuries, for which we need not help but should definitely help by not ruining in any sort. Please respect the age-defying monuments any where for which the whole world admire them!!