Q&A for How to Make Yeast

Once the fermentation is going, you can skim the foam from the surface of the bowl. This will have active live yeast in it. From there, you might want to put it in a secondary culture of flour and water to increase the size of the culture before you pitch it into a batch of bread dough.

Keep it overnight. However, it depends upon climate. If it is hot it will take less time to ferment and if it is cool it will take more time.

30 - 40 degrees Celsius (86-104º) should be sufficient. The 'optimal' temperature is 38 degrees Celsius (100ºF), but shouldn't matter too much.

No, wine is distinctly made from grapes. Wine is made from the fermentation of grape skins or pulp. Potatoes have no pulp and they are not grapes; however, it is possible to make another alcoholic drink from potatoes, just not wine.

That is a more complicated question than you may realize. A good book on the subject is "How to Brew" by John Palmer (the first edition is free online). The information is obviously geared toward brewing, but the information about how yeast works is applicable to baking as well.

If you have barley, you can sprout it. You can also use whole grain flour and sugar as a replacement.

Refer to Method 2.

Allow the water to sit in an open container over night. The chlorine will evaporate out of the water at room temperature.

Use about 1 part yeast to 1000 parts of flour by weight (this may vary depending on recipe, or preference).

Overnight typically, though depending on temperature or humidity it can vary. Hotter, and/or more humid, it will be done quicker. And if colder and/or less humid, it will take longer.