It's important to have water free from chemicals, specifically chlorine as it may damage the starter. If you have city/tap water (versus your own well) you can place a jar or bowl of water, uncovered, out on the counter overnight. You can also boil the water for ten minutes and let cool to room temp.
Day one through day four you are going to place 1/4 cup of flour and a scant 1/4 cup of water into a jar and stir with a wooden (or plastic) spoon every morning and every night. I find that when making a starter, it's helpful to feed it twice a day for the first few days. Cover your starter with a thin towel or cloth jar cover. (I've also used coffee filters and rubber bands which work well)
If your starter doesn't seem very active, you can "boost" it a bit by adding a tablespoon of water kefir.
By day five your starter should be bubbling along and able to sustain just one feeding per day, so each day you add 1/2 cup of brown rice flour and 1/3 cup of water. The consistency we're looking for is going to be like cake batter, so add more or less water based on how yours looks. (the current humidity will affect how much water you need to use)
At day seven you should have enough starter to make your first sourdough recipe!
It is important to keep your starter in a warm place; if it gets too cold it won't be active enough to work. I find that keeping mine in the oven with the pilot light on can help immensely during the cold winter months. Others find that they can place it next to the stove or on top of a refrigerator for warmth.