Start with a clean glass container. I prefer to use a quart size mason jar with a plastic lid. (You don't want to use metal because it can rust overtime and contaminate your starter.)
Add in the warm water, then add in all of your dry ingredients (sugar, potato flakes, and yeast)
Stir with a wooden spoon. (I always suggest to use wood because a metal spoon could react with the ingredients. However, I almost always use a metal spoon and have never had any problems)
Cover your container with a loose lid, or a tea towel with a rubber band. You want it to be able to breath. At this point, do not refrigerate the mixture. Leave it in a warm place at room temperature so the yeast and good bacteria can begin to feed.
Leave it at room temperature for 4 days, stirring daily.
On the morning of the 5th day, you will feed the starter. Add in 3 tablespoons of instant potato flakes, 3/4 cups of white sugar, and 1 cup of lukewarm water.
Stir the starter and ingredients you added and continue to let it sit out at room temperature for at least 6-8 hours. (I usually do this overnight)
Once the starter has sat out at room temperature for 6 to 8 hours, stir your starter well to incorporate anything that has settled or risen. Remove 1 cup of the starter to make your bread. You will then place the rest of the starter in the refrigerator.
Feed the starter at least once every week or two to keep it nice and active. Do this using steps 6 through 8.