The birthplace of pilsner
The pale, golden lager style now brewed everywhere in the world as "pilsner" was first made in Plzeň, in what's now the Czech Republic, in 1842. That heritage is a source of real local pride, and Czech pilsners remain some of the best in the world by any reasonable measure — this isn't marketing, it's the honest starting point for understanding why beer matters here more than in most cities you'll visit.
How a traditional pub actually works
Don't expect a menu of thirty rotating craft options — many classic Prague beer halls serve one or two beers, brewed properly, and that focus is the point rather than a limitation. Waiters often simply keep bringing a fresh beer as your glass empties unless you signal otherwise (a coaster placed over the top of your glass is the usual way to say "no more"), and your order is tracked with tally marks on a paper coaster at your table rather than a running tab you have to request.
Settling up happens when you're ready to leave — ask for the bill (účet, prosím) rather than waiting for it to appear automatically. Tipping is customary but not obligatory, roughly 10%, handed over directly when you pay rather than left on the table.
What to actually order
A classic čepované (draft) pilsner is the safe, excellent default almost everywhere. Beyond that, look for a tmavé pivo (dark beer) if you want something maltier, or ask what's brewed on-site if you're in one of Prague's growing number of brewpubs. Food-wise, a beer hall is the natural home for the hearty dishes in our Czech cuisine guide — guláš and dumplings especially.