1. Your ward number (http://bbmpelections.in/wards),
2. Google translate (from kannada to english & vice versa) - had a tough time choosing occupation :D,
3. Electricity bill
4. If you have an Indane or BP gas connection, a bill
Took about 40 min for me, as I can't read Kannada alphabets. Had to select my occupation 10 times, press forward (to see with my horror that either I am an agri. laborer or a potter) and then come back to reselect another option.
Big advantage - no need to go to Ration card office, just submit online and wait for verification (with proofs). Enjoy maadi!