Purchase seven, 20 by 10 inch seed trays. The trays should be approximately 2 inches deep. This will yield approximately 1 oz. of wheatgrass juice per day, according to Juicing for Health.
Soak 500 g of wheatgrass seed overnight in a bowl filled with water.
Fill each tray half full with potting mix.
Spread the seeds on top of the soil in a single layer. Cover the seeds lightly with a small amount of potting soil. Use just enough soil to cover the seeds.
Apply a small amount of water on top of the soil. The soil should be moist but not saturated.
Cover the tray with moist newspaper or plastic wrap and set it in a warm sunny location -- such as a windowsill.
Uncover the tray and water the seeds daily to keep the soil moist.
Remove the cover after three days when the grass has reached a height of around 1 inch.
Harvest the wheatgrass when it has reached a height of 7 to 8 inches tall.