I keep about 50 gms of starter. I never feed it until I want to make bread. It can sit in the fridge for weeks before I need it. When I want to make bread, I feed it so that the amount of water and flour that I add to the 50 gms is slightly more than I need for the recipe. If I need 100 gms of starter, then I feed it about 55 gms of flour and 55 gms of water. Then I’m back down about 50 gms of starter. I never discard. So wasteful. Go to foodbodsourdough.com. She even has a YouTube video. There is also a group on Facebook called sourdough for beginners. So many helpful hints are available.

The more you make bread the more yeast spores are in your kitchen. There are good and bad yeast and you want the good strain. Keep making bread and you will have terrific starter going all the time. Back in the day I was a big fan of homesteading. I read everything there was on self sufficiency even though I never lived on a homestead.

I save a couple of cups of water from boiled potatoes to make sandwich bread the next day. I add some yeast to the warm (not over 115 degrees, warmer will kill the yeast) potato water and let it sit over night lightly covered. I add about 1/2 teaspoon of sugar about 1/2 hour before using to be sure it is active. It will get all bubbly.

You can make starter out of the whole potatoes too.

That's pretty much what I do, except I never measure. I've done it for so long that I can pretty much gauge it by eye.

I never discard. So wasteful.

What is wasted but a small amount of flour? I don't understand.

Some people keep a large amount of starter and feed frequently even if they are not going to bake. If you are going to feed frequently and not use up the starter, you have to discard otherwise you will have quarts of starter. It’s a misconception that starters have to be fed frequently to keep it alive. The starter can sit in the fridge for weeks, not be fed, and not die. I only feed when I want to bake and that’s not even once a week.