I must confess, even though it is technically a form of cooking/baking, maintaining and growing sourdough cultures satisfies my biologist itch.
Sourdough starters are cultures of living organisms. Mixtures of wild yeast and your local lactobacillus strains ( these bacteria are what gives it a “local” flavor and the sour taste).
The even better news is that they are organisms that tolerate small amounts of stress reasonably well and can be “slowed down” in the fridge ( or even dried and frozen) for periods when life is crazy and daily maintenance is impossible.
Like all microorganisms, a culture can quickly grow beyond useful size… so it is most important to understand what your goals are to set the right feeding schedule.
There are lots of recipes that use sourdough starters- not just bread. Some of my current favorites include waffles, pancakes and muffins! 
Recipes usually call for 1-3 C of active starter ( this is starter that is actively growing and bubbling). If you know how much starter you need, you will know how often to split and cook with the split along the way ( you can also certainly just discard part of it, although that always breaks my heart). If you do not have time to cook with your split discards, this is also a great time to inoculate friends and neighbors with their own potion of the starter.
Feeding is adding equal mass flour and water to your starter daily to give the microorganisms new food to continue to grow and divide. I find right now, if I add about half as much new total volume as the existing culture, then the culture grows well. We are not yet into the heat of summer, so I expect this ratio to change. The most important thing is to watch and listen to your culture- is is bubbling nicely? Then it is happy and growing.
Has the bubbling slowed down? Then it is unhappy.. try feeding it a bit more. If this does not help, look at environmental factors… was there a temperature or humidity change? Don’t worry about experimenting a bit.
If you think about the math, you will quickly see why you need to split and use/discard frequently.
Day 1: Start with 2C fed starter
Day 2: feed with about 1Cup flour/water combination. – total about 3 C starter
Day 3: Feed with about 1.5 C flour/water combination – total 4.5 C starter
Day 4: Wait a Minute.. just how much starter do you need? 4.5C is probably already more than most people need.. but maybe you are ambitious. But do you really want to feed the whole danged thing and have almost 7C starter now?
This is a good time to SPLIT. Keep just 1 -2 cups of original starter, feed that and then use the discard for something delicious– or just add it to your compost heap.
Day 5: ( see Day 2)
And so on….
if you have a busy week in the rest of your life, or you will be traveling and not around to love and care for your starter, you can happily put an active culture into the fridge and go a week between feedings. Make sure you put a recently fed culture in, so it has plenty to slow gnaw on over that slow week.
