Yercaud Experience: This is a good place for a short trip.Cheap place to stay would be Hotel Tamil Nadu.Do visit Kiliyur falls.Little steps to climb back,,but worth it.
Food, sight-seeing and shopping: Nothing great to EAT
Activities & things to do: If comin in car. do Ask locals for direction to see all points.
If you have to depend on rickshaw,,pay 300 Rs & check thewhole place out.
Travel tips, How to reach, travel warnings etc: Salem to Yercaud there are busese every half an hour.