cultivation of water melon is very much same as pumpkin.
Sow the seeds in ventilated plastic cover. plant them on flat ground with space of 6 X 6 feet after three weeks. Watermelons are very sensitive to lightning.
Best time to grow this is between December and early March (Bangalore climate condition).
It is easy crop to cultivate and your crop should be first or last in the market. If your produce is in between, there will be lot of supply and Profit will not be huge.
Plan correctlly prior to 100-110 days and Plant Watermelon and get good profit in short span