Check your lunar calendar for full moon dates in late April or early May. Note that each day after each full moon, the moon appears slightly smaller until the dark of the moon, or new moon phase.
Choose a planting date near the center of the waxing moon phase. Too much light from a mostly-full moon may hinder your efforts, as will the dark sky of the new moon. You want just a little, waning light for your potatoes. Choose the day of the waning gibbous or waning half-moon.
Push a motorized tiller 6 inches into your soil the day of your choosing. Picture the day and the night as a full day, with the day coming before the night. For instance, if you chose May 10 as the best moon conditions, till the soil on the day of the 10th, not on the 11th.
Plan to have all your potatoes planted before sunset on your chosen day. Planting in the dark is dangerous and planting on the wrong day affects your crops.
Plant your seed potatoes quickly, burying them in the soil about 6 inches apart, in rows about 10 inches apart. Cover them with soil and press down firmly.
Water your potatoes before sunset on the first day. About 1 pint of water per potato should be enough.