Some websites out there try to over complicate it by telling you that you have to use a certain kind of flour or that you need to buy unchlorinated spring water. You don't need to do any of these things. The only exception would be if your water has so much chlorine that it smells like a swimming pool. In that case, you might want to use bottled water.
All you need to do to make your starter is simply mix equal parts of flour and water in a plastic or earthen bowl. Metal is not recommended because it can be reactive. Although I suppose stainless steel might be OK since it's non reactive, I've never tried it though. An enameled bowl would work as well.
I started mine with two cups of white flour and two cups of water. Once it's mixed together well, cover it with some sort of cloth. I use either a tea towel or a large dish cloth. If the air is really dry, you may want to dampen your cloth. I have learned in the winter that if I do not use a damp cloth, I get a hard crust on the top of my starter. This does not harm the starter in any way, and when it happens I simply take it off and feed it to the chickens.
How quickly your starter will be active depends on the amount of wild yeasts in your environment. When I start a new starter I see bubbles overnight and have a full active culture within three days. For some it takes up to a week. When your starter is ready it will look like this:
You can use sourdough for a lot of things and I will share some recipes with you over the next few days. We love to use it for pancakes and biscuits.
As much as I love sourdough, I have never made bread with it. So today I'm trying my hand at that. Here's the beautiful dough I have sitting out to rise as I type: