There is no shortage of sourdough guides on the internet, and most of them make the same mistake: they assume you already know what a starter looks like when it is hungry. We are going to walk through one full week with photos and timing for each day, so you have a clear picture of what success and failure look like.
Day one is the easiest. Combine 50 g of whole wheat flour and 50 g of warm water in a clean jar, stir with a chopstick, and leave it on the counter loosely covered. You will see almost nothing for 24 hours, and that is fine. By day three you should see small bubbles. If you see no bubbles, do not panic, just keep feeding twice a day at 12-hour intervals.
By day five your starter should be doubling between feeds. You should be discarding most of it, keeping only 20 g, and refeeding with 40 g flour and 40 g water. On day seven, do a float test: drop a teaspoon of starter in cold water. If it floats, you are ready to bake. If it sinks, give it two more days. Patience here pays off in every loaf you bake for years to come.