Boiling the Water
When seawater evaporates, the droplets no longer contain salt, making evaporation the easiest way to separate water and salt cheaply and efficiently. One way to catch the clean, drinkable water from the evaporation of salt water is to use an open source of heat such as a flame or stove top. You will need to pour the seawater into a pot and let it boil over the heat. Instead of putting the lid on the pot, place a clean cloth or towel directly above the pot, where it will soak up the evaporation. Once the cloth is saturated, you can remove it and wring it out into a separate container you wish to drink out of. You may have to saturate the cloth several times to get an adequate amount of drinking water.
Using Dishes and Sunlight
Another way to desalinate seawater is to use dishes and supplies most people already have in their kitchen. Unlike boiling the water, this method only requires a one-time setup and is much more efficient. Building the device is simple. First, fill a flat-bottomed plastic dish or bowl with salt water and set it outside on a sunny day. Place a saucer upside down in the bottom of the flat-bottomed dish, and then place a glass on top of the saucer. Cover the entire dish or bowl with plastic wrap, but allow a bit of slack. Tape the plastic wrap down, and place a coin or stone in the middle to weigh it down. As the sun beats down on your device, the water will evaporate and condense on the plastic wrap. Since it is weighed down in the middle, the evaporated water will drip toward the weight and drop into the glass. The evaporated water does not contain salt; therefore the water in the glass will be drinkable.
Using Juice Containers and Straws
If you don't have the materials to build a desalination device out of dishes, you can use alternative materials such as juice containers and water bottles. You will need to take one 2-liter juice container, such as the plastic ones fruit punch comes in, and cut out one side using a utility knife. Pour the salty water into the juice container. Also use the utility knife to cut the top off a plastic water bottle. This will be your collection cup. Place it with the cap side down; secure it in place with tape if necessary. Wrap plastic wrap over the cut-out side of the juice bottle, leaving some slack and taping it in place. Place the juice container, plastic wrap side up, on a flat surface where it is in direct sunlight. On top of the plastic wrap, place a small weight like a coin or stone. Place a piece of foil on the opposite side of the container that is facing the sunlight to attract extra heat. When left for several hours in the sun, the seawater will evaporate and condense on the plastic wrap and drip toward the weight in the middle, falling into your collection cup.