You can book your luggage either on your ticket or as a Parcel. You need to go to the source station well before the departure of the train and reach the parcel section (not sure what they are really called). Ask them that you want to book the luggage as a parcel. They'll do some formalities and ask you to write the worth of that item (if in worst case they are lost). There would be People just outside the office who are willing to pack your items for the transit. They'll take some ₹ 200-300. The railway clerks will make a bill with net cost and will take your parcel. Now it's Railway's duty to load your parcel on the train but to be on the safer side do come back to the station about 40 mins before the departure and check if your parcel is properly loaded or...
more... not.
At the destination station again go to the parcel office and show that slip and they'll hand over the parcel back to you.
Hope it helps!