Buying new packets of yeast quickly becomes an expensive proposition. Cleaning your primary fermenter, you've washed massive amounts of yeast and gunk down the drain. Professional breweries use that yeast to ferment the next batch. As a homebrewer, you can repitch your yeast and you can skip starters for high-alcohol monster beers.

If you trust your sanitation procedures completely, you can dump your freshly chilled wort straight into the unwashed primary fermenter. For everyone else, sanitize a few growlers or mason jars and boil some water. Fill the jug with your fermenter sludge and add some of the boiled water. After an hour or so, you're left with a jug of settled gunk and a beige liquid yeast layer. Pour the liquid into a second jar along with a little more water and watch it settle into creamy yeasty goodness. Reuse quickly (within a week) before the yeast dies off!