In general, when booking your flight to New Delhi, March is the cheapest month on average.
From most locations, booking your flights to New Delhi around 60 days prior to your departure date finds the best deals.
On average, the cheapest flights to New Delhi are found when departing on a Wednesday. Try to avoid departing on a Saturday, as this is usually the most expensive day.
On average you can find the best deals on plane tickets to New Delhi when looking for flights with evening departure times.