Purple Majesty
Blue Potato in the US

You'll want to get your seed potatoes chitting a few weeks before your last frost date, you know, let them sprout a bit in a cool, light spot. Then, depending on your USDA zone, you'll be planting them out from January right through to May. Zone 3 folks might wait until May, while those in Zone 9 can get cracking in January or February. For example, Zone 6 can plant in March or April, and Zone 8 in February or March. Plant them about 4-6 inches deep (10-15 cm) and give them about 12-18 inches (30-45 cm) between each one in a row. They like a good bit of space to spread out, so direct sowing is the way to go.

Once your potato plants start to grow a bit, you'll need to 'hill up' or 'earth up' the soil around them. This protects the developing tubers from greening in the sun, which can make them bitter, and encourages them to make more spuds. Keep doing this as they grow, piling the soil up around the stems until they're a good foot (30 cm) or so high. Make sure your plot has good drainage, especially if you're growing in containers, to stop them getting waterlogged.