Mix vaguely equal parts of flour and non-chlorinated
water together in a jar/crock, whatever (jars are easier to store). Put an unwashed organic grape or berry in it, and stir it every day, vigorously. A few days into it stir a few more table
spoons of flour in it.
In about a week (at that point find the grape/berry and remove it) it should smell sour and be bubbly, the signs of yeasty life - and will henceforth be known as a "starter!"
If you don't have time to use some of your starter more than once a week at the least, store it in the refrigerator. I'd give it a new clean jar/container every so often to prevent mold, the number one enemy of sour dough starters.
I've never heard of freezing it....I feel like the yeast would survive but the bacteria might not appreciate it as much. But I have no
experience with frozen starter, so listen to those that do!
Unless you like very thin pancakes you'll probably want to pour out some of the starter from your jar a night or two before making pancakes, and in a bowl create a pretty thick paste by adding more flour, to which you can add eggs and the rest of the pancake stuff the morning of cake making.
You'll get better at guessing what consistency is perfect before the addition of egg(s) (very wet ingredients). It's easy to thin out an overly thick batter with a little
milk or water, but adding raw flour as a thickener quickly diminishes the sour flavors.
Whenever you pour some of your starter out of the jar/crock, replace what you took with more flour and water. I sometimes leave very little of my starter in the jar (as in, what sticks to the sides when I pour everything out), doesn't seem to be a problem for recolonization. Some people are more cautious about the amount of starter they leave behind - no more than two thirds taken out or whatever. Shrug.
I've had my starter for over a year now, recently named her "Henrietta." We eat sourdough pancakes, waffles, crepes, or some other incarnation of fried sour batter almost every morning. I don't use baking powder/soda, the dough itself has plenty of rise for our tastes.