It is agreed that buying certified seed potatoes is best to help avoid any potato diseases or viruses that could be present in regular store-bought potatoes. These viral problems can get established in your garden soil and cause problems to re-occur for many future years to come. Store-bought potatoes are usually treated with chemicals to keep the potato "eyes" from growing so that they last longer in your storage area.
After you purchase your potatoes there is no real need to hurry and plant them. It is actually a good thing if the "eyes" start to grow, just a little before you plant them into the ground. Simply lay them out in an area where they are warm and somewhat dark for up to two weeks. The soil should be fertile by working in some composted materials such as cow manure or mushroom compost. Potatoes like calcium-enriched lime but not at the same time. Lime should be applied in the fall for the following season, not for the same year or scab could occur.
Plant your potatoes as either the whole potato with the growing "eye" facing upward or cut the potato into a couple of pieces facing all of the eyes upward. Interesting enough is the fact that everyone always wants to get the job done real early but the proper time is when the soil temperature reaches between 50-70 degrees, or just when you see dandelions coming into bloom. Plant your potatoes 4" to 6" deep and 10" to 12" apart. In a row 6' long, use one pound of potatoes...2 1/2 lbs. in a 12' row, and so on.
As the potatoes grow, hill the soil up around the plants so that only the tops of the plants remain visible. Repeat this hilling process so that your potatoes end up around 12" to 18" deep. The potatoes actually grow from the stem and not the root as most people believe so it is important to get them buried deeply. Adding straw after the hills are finished helps keep the potatoes cool and keeps the weeds to a minimum. Potatoes are shallow growers so watering is a must. Only stop watering 2-4 weeks before harvest.
Disease control is needed from late summer blight when the night-time temperatures drop back into the 50s and you see dew on the grass in the mornings. This blight can destroy your potatoes and tomatoes in just 3 to 5 days so be ready with your preventative fungicides. This is another reason why watering early in the day is so much better than in the late afternoon. Keep the foliage dry in the evening.
Expect to harvest your potatoes as early as 60 days after planting, although these will be babies and you should harvest just a minimum of these so as to not cut into your real crop. When the tops of the plants start to die back, your potatoes are mature. Wait another 2 weeks, then harvest. Allow the potatoes to time to dry, then brush off the soil. Do not wash before storage. Place in an area with temperatures between 36 to 40 degrees with plenty of air circulation. Put them into bushel basket, wooden crates or burlap bags for best air movement.
Best variety for baking or fries is Russet; for mashing is russet or Yukon gold; for steam/boiling are red Norland, red Pontiac, Irish Cobbler or Kennebec; or as an all purpose potato are Yukon Gold, Superior or Kennebec. Although these are just guidelines, I have never meet a potato I didn't like. Look for these varieties when shopping for seed potatoes.