As Surya is partially malefic (Krura Graha) by its nature, thus Sunday generally is considered to be a day for either for Paapa (sinful, unethical, cruel actions) or some Shubha (auspicious) Karmas
only if certain benefic work isn't specified for it. Its nature is
"fixed & stationary" (in ancient Sanskrit - "Dhruva" or "Sthira"), thus all "fixed & stationary" works are
good on Sunday. In combination with "fixed & stationary" Nakshatras (Rohini, Uttara Phalguni, Uttara Bhadrapada, Uttara Ashada) activity related to this Nakshatras will be very fruitful. As for effectiveness - Sunday
is effective during day-time. This day is auspiscious for everything
related to copper-red, blood red, sunrise colour, government, father,
king, ego, self-esteem, truth, Sattva, cleariness, health etc (as Surya,
a ruler of this day, rules all these things). All works that somehow
are related to destroying something on the way to light or getting
health are very auspicious (as Shiva, who's responsible for destroying all obstacles on the way to Moksha is a tutelary Devata of Sunday. It's very auspicious to appeal to Shiva while trying to do something important during Sunday). Adhi-Devata of Sunday is Agni, who's very similar to Surya by its nature. Thus, Sunday is a very auspiscious day for anything that's related to Agni, fire, light and all similar things.
Basing on mentioned parameters works in following fields are especially prescribed for Sunday: coronation, service to government / king, worshipping of king, service & employment; works related to fire, weapon making & usage, war, bravery, travel, thief catching; doctor, transaction of medicine; purchase of cows, bullocks & animals; works related to gold, silver, copper, wood; bones-skin-hides, Manglik (auspicious) works, Yagya, teaching Mantras (Agni Mantras), religious discourse, music learning; wearing of new clothes, woolen clothes; mountain, stones, dessert, forest, trees, usage of forest items; snake, animal rearing & husbandry; food grain; trade.
