Learning how to feed a sourdough starter takes a bit of practice. The more you work with your starter, the better you’ll understand how to feed it.
It is helpful regularly take notes on how you feed your starter to better understand what worked and what did not work - whether you are super detailed (temperature of water and room, etc.) or simply recording the feeding and waiting times. Both options will help you determine what works best for your own sourdough starter.
If you plan to bake often, you should feed your starter daily. We feed our starter almost twice each day, but that’s typically unnecessary at home. If you are not going to use it right away – put the date on it and keep in the fridge. Discard some and feed once a week. Ideally, you want to have the starter less than the 1:1 ratio of flour and water (which then becomes your new batch of starter).
If you have been discarding and feeding your starter that has been on the counter, maintain about 65g for making a loaf of bread and having some for next use after feeding.
For example, if you have 30g of starter – discard 10g and feed 30g water and flour each. This will give you 80g of starter – enough for a loaf of bread (60g) and remaining to feed for future use (30g).