Watermelons are a warm-season crop and are best planted in the early spring when the ground is warm and the chance of frost has passed. Since the watermelon has a fairly deep root system, the plants don't require a lot of extra water when planted in the garden. Normal rainfall conditions will supply your watermelons with the appropriate amount of water unless you're experiencing a drought. During periods of drought you should water the plants at least once a week until the dry weather passes.

Start watermelon seedlings indoors 3 weeks before you want to plant them in your garden. Make sure you plant the seedlings at least 6 feet apart to allow the plant to grow and expand. Watermelon plants prefer sandy loam soil and--depending on the variety of watermelon you've planted--are normally ready to harvest 70 to 85 days after planting.

For more information on growing watermelons, check out these sites:

Growing Watermelons in the Home Garden:
http://ohioline.osu.edu/hyg-fact/1000/1626.html

Watch Your Garden Grown Watermelon:
http://urbanext.illinois.edu/veggies/watermelon.cfm

There are different varieties of watermelons. First thing is you need to decide which variety to plant. Some of the most popular varieties of the herb are the Charleston Grey as well as the Sugar Baby. Next, choose a location to plant the watermelon. Choose an area that has some sandy soil. The best time of the year to plant watermelons would during warmer climate. Also the place where you plant needs to have exposure to sunlight.

Source : http://www.deartips.com/tips-growing-watermelon.html