What's worked for me: Do not eat anything on the journey over. Yes - both your flights if they're connecting [unless pre-existing health conditions require you to eat]. Food throws off your clock. Next: Sleep the entire time - pop a melatonin or a couple Advil and close up shop. An eye mask should help. Yes - you can drink water during the journey. Finally: When you arrive, depending on the time, stay up as long as possible until it's a "reasonable" hour to sleep [think... 8pm onwards]. Ladies: I usually throw on a hydrating facemask on the last 2 hours of the journey until I reach India. Your skin will thank you! Example: You arrive at 2pm IST. Stay up for the next 6-8 hours! You will need to use some will power to get through this. That is normal and this is possible. Next day your jet lag should be cured!
At least a day in advance! That means at the latest, December 31st - if possible, plan to arrive earlier in the day!