There are lots of different ways to make and maintain your own sourdough starter. Some people swear by using pineapple juice, some people only use rye flour, the list goes on. As long as you have flour, water, and wild yeast, you've got yourself a starter.
Basically, a starter is a combination of flour and water that will attract and feed wild yeast and bacteria. Once your starter is established, you can add it to a dough to naturally leaven it and add more flavour. Depending on the hydration of your starter (ratio of water to flour), the flavours will be different because it will cultivate different bacteria.
Your starter will take about 5 to 6 days to become established and needs to be fed at roughly the same time everyday. Factor this into your schedule when you make your starter.
I am using the Tartine Bread starter recipe simply because the hydration is 100% and I prefer the milder sour flavour it gives.
Making a Starter
First, mix 5 pounds of bread flour - half white and half whole wheat. You will use this 50/50 flour blend to feed your culture and develop your starter. All-purpose is okay as well.
Fill a small, clear bowl halfway with lukewarm water. Add a handful of the 50/50 flour blend to the water and mix with your hands to achieve the consistency of a thick batter with no lumps. Use a dough spatula to clean the dough off your hands and tidy the inside of the bowl. Cover the bowl with a kitchen towel and place in a cool, shaded spot for 2 to 3 days.
After 2 to 3 days, check the culture to see if any bubbles have formed around the sides and on the surface. If the culture seems inactive, let it sit for another day or two.
By this time, a dark crust may have formed over the top of the mixture, which is typical. Pull the crust back and note the aroma and bubbles caused by fermentation. In this initial stage, when the culture smells strong like stinky cheese and tastes sharply acidic, it is very ripe. Now it is time to do the first feeding.
To feed the culture, discard about 80% of it. Replace the discarded portion with equal amounts of water and the 50/50 flour blend. Mix to combine just as you did in the beginning. You have now begun training your culture into a starter.
Repeat the discarding and feeding process once every 24 at about the same time each day, preferably in the morning. Don't worry too much about the quantities of water and flour in these feedings - you want a thick batter. The important thing is that you feed the starter and pay attention to its behaviour as it develops.
As the balance of yeast and bacteria is established, the volume of the starter will increase for several hours after feeding and then begin to collapse as the cycle winds down. Note how the aroma of the starter changes from stinky and sharply acidic to sweet and milky just after feeding, when the starter is at the freshest or youngest stage in the cycle. When the starter ferments predictably - rising and falling after feedings - you are ready to prepare a leaven and mix your bread dough.
Keep in mind that training your starter is a forgiving process. Don't worry if you forget to feed it one day; just make sure to feed it the next. The only sure way to mess up a starter is to neglect it for a long period of time or subject it to extreme temperatures. Even then, a cycle of regular feedings will usually restore the vitality of your starter.