Methods and Rationale for Sourdough Starter Maintenance and Elaboration
Since the facility for uploading fully formatted Word and PDF documents has not been implemented, the details of this post can be found here and I have loaded (above and below) a pictographic shorthand version which lacks any explanation of the rationale. The artwork covers the whole bread-making process of which the illustration above covers starter maintenance, elaboration into a levain, and then using the levain to initiate a batch of bread dough. The linked paper covers only the starter maintenance and elaboration aspects of this process. The remainder of the complete bread process is included in the illustrations below.
One point I want to make here is that you don't need to keep a lot of starter, even if you want to make a lot of bread. Using the quantities noted below, you are keeping about 30g of starter, from which you use 3g to seed a refresh cycle and either throw out the remainder or use it to make a levain, from which you will make a batch of bread.
Many sources would have you keep at least a cup of starter (or a pint, or a cup in a pint jar, or a pint in a quart jar) which is totally unnecessary. If you are going to need 10Kg of levain, you can elaborate 20g into 10,500g in two steps (or 3g into 10500g in three steps), building 20g into 500g of refreshed starter by feeding it at 20:250:250 (a factor of 12.5) and letting it ferment for 6 to 12 hrs depending on the temperature and repeating the feeding to expand it by another factor of 10 (500:5000:5000) to yield 10.5 Kg of levain. So your little 5.5 oz polypropylene food service cup containing 28g of starter becomes 10.5 Kg of levain in 24 hrs. By doing this and assuming that you feed it every day (which is one option though once a week is enough to maintain it if you don't need bread during that time) you throw out starter containing ~16g of flour every day. That is a total of over 5.5Kg of flour in a year which is not trivial, but it does make for a pretty inexpensive hobby - or you might perfer to think of your starter as a pet which doesn't eat nearly as much as a dog. If you maintain a pint of starter and feed it 50g of flour daily you will need 18Kg of flour over the course of a year in addition to the amount you use to make bread. And you have to figure out where to throw out 100g+ every day (which should never go down the drain since it will eventualy coat your drain line like hundreds of layers of paint and irretrieveably plug it up).
You can also read the blog post down below the one about idli that explains the The 2% weight loss method for judging levain maturity (which you can also use for your starter if you have a high accuracy scale).