Most stores sell this delicious probiotic beverage for $3.50 to $5.00 a quart. I make my own for 0.55¢ a quart. Make great fruit smoothies, use in baking, or drink it straight. You have a fresh batch every 24-48 hours.
Acquire Kefir grains* from a friend or sometimes they are available on Amazon or Craigslist. If you receive from a friend, they will probably come to you in some finished Kefir, which you will strain using a colander with smaller holes (1/16" or so). The liquid that goes through the strainer is finished and ready to mix with fruits or whatever you want to do with it.
The material that does not go through the strainer is the kefir grains. Place them into the container you are using to make a new batch.
Warm the milk to about 77°F. Use fat-free, or whatever you want. Pour into jar with Kefir grains and cover.
Keep the covered container of grains and milk in a draft-free, room temperature, out of sunlight setting. In 24-48 hours you should notice that it has set up, or thickened when you gently shake the container. Pour contents through the strainer and repeat this process to start your next batch
*Kefir grains are not from grain. Grain is simply a reference to their granular shape. They also resemble small pieces of cauliflower or cottage cheese.