I'm honoured to be part of the thread title and bread's come up in the I'm fucked megathread so synchronicity says it's time to write down a simple guide on....
How to make your own slow motion tamagotchi (aka sourdough culture)
Strong Flour
Water
A wide mouthed jar with lid (0.75l should be ample)
What you're doing here is trying to capture and cultivate wild yeast. If all goes to plan the yeast will colonise the jar fast enough that they force out other funghi and bacteria and keep them out permanently. The yeast need food (flour) and moisture and a reasonably warm temperature to get going. They need food and water from time to time to keep going. The yeast may come from the air, you or the flour you start the process off with. Wholemeal flour is often recommended as a starter as it is meant to contain more live yeasts but I've done this with regular white/brown bread flour.
Put about a cup of flour and a cup of water in the jar, leave jar with lid off. If you can be arsed use mineral water or another source without chlorine but it works fine with tap water IME.
12hrs later discard half and top up with flour/water.
12hrs later look for signs of yeast, ie bubbles, the whole shebang 'rising' a bit and a beery smell. Either way discard half and top up with flour/water again. If no bubbles / beery smell, continue with the 12hr waits / top ups until you either get to the beery stage or get bored / forget about it.
If you have got to the bubbles / beery smell stage you've arrived. Top up the jar til about 3/4 full with 50/50 flour and water.
Refrigerate the jar making sure you leave the lid resting on the top so that co2 can escape. The fridge slows down the yeast so that it doesn't poison itself with alcohol too fast. You can feed it every ten days or so by discarding about 1/3 - 1/2 of it and replenishing with fresh flour and water. You may also tip off any brownish liquid which forms (this contains excess alcohol). Keep it wet, should be sloppier than dough but dryer than soup.
To use in recipes take out about 1/3 - 1/2 and mix with flour, oil, salt and whatever else is in your bread, replenishing the jar with as much flour/water as you've taken out. Leave dough overnight to rise (this takes longer than with commercial yeast strains). Bake as per your bread / pizza recipe. Look up sourdough recipes online for more info.