This legendary Sapporo attraction is in the original Sapporo Beer brewery, a pretty, ivy-covered brick building. There's no need to sign up for the tour; there are plenty of English explanations throughout about Japan's oldest beer (the brewery was founded in 1876). At the end there's a tasting salon (beers ¥200 to ¥300) where you can compare Sapporo's signature Black Label with Sapporo Classic (found only in Hokkaidō) and Kaitakushi Pilsner, a re-creation of the original recipe (found only here).
Afterwards, head next door to the Sapporo Biergarten for more beer and jingisukan (all-you-can-eat lamb dish). Note that any drivers will not be allowed to drink.
From the subway it's a 10-minute walk; the bus stops right out front.