We love our snap peas here in the squibix household! Aside from how good they taste, it's wonderful to watch the vines grow so vigorously early in the season. We haven't had any success with shelling peas, but I'm sure we'll try again one day.
Scatter over a 6-inch wide area, one inch deep. Use legume inoculant. Protect seedlings and even mature plants from small animals. Provide strong support for vigorous cultivars like Super Sugar Snap.
It doesn't really make sense to buy pea seedlings: it would take at least half a dozen six-packs to make a reasonable crop. Some people report success starting their peas inside but we've had good luck with quick outside germination so we haven't bothered yet.