Today is day 3. You should see some bubbles and it may smell slightly fruity. This means that it’s working. Don’t worry if this isn’t happening yet, it will. Today you’re going to start feeding your starter twice a day. Try to do this at approximately the same time every day.
You’re going to remove about ½ cup of the starter after you’ve stirred it and toss out any of the rest of the starter (see tips below for what you can do with removed starter if you don’t want to be wasteful and throw it out).
Add another 1 scant cup of flour to your remaining ½ cup of starter and again, ½ cup of warm water.
Mix well and allow it to sit for about 12 hours and repeat the same thing. Remove all but half the starter, add 1 scant cup of flour and ½ cup of warm water.