When to help a rabbit;

If the rabbit has been hit by a car

Rabbits that have been hit by a car must have medical attention as soon as possible.

If you are certain it is orphaned      
If you can see that the burrow is totally destroyed, for example, dug up or flooded out completely then the babies must be taken in because the mum will not return.

If one or more legs appear damaged
Rabbits need all four legs to be in good working order.  Any fractures need to be treated as soon as possible, at a rescue centre.

If it's dragging both hind legs
Can indicate a spinal or pelvic injury, handle the rabbit very carefully, preferably on a board, and take to a wildlife rescue centre immediately.

If the rabbit has open wounds
Open wounds can become infected and will not heal without assistance.

Any "apparent" orphan showing an injury
Orphaned animals that are injured will need medical attention at a wildlife rescue centre.                 

Rabbits will kick with their back legs but have very weak back bones so always support both ends of the animal. Once you have established that a rabbit is in need of assistance, pick it up and put it in a cardboard box. The box should be lined with newspaper and a towel. You can also add a hot water bottle, wrapped in a towel, (or any plastic bottle filled with warm water) to the box, as direct warmth will help an animal that is suffering from shock. The rabbit should then be taken to a wildlife rescue centre as soon as possible.