Most "coffeeshops" will somewhere have a sign with the appropriate shape of leaf or some variant of yellow/black/red/green stripes or flags.

A conventional café will call itself a café, and you are more likely to hear Dutch or German 'Schlager'-style pop rather than heavy-duty beats. There may be lots of photos of regulars in party costumes, memorabilia of favourite sports teams, and/or a wall full of foreign banknotes. For the really traditional Amsterdam "brown café" experience, look for some combination of that special Dutch sort of swirly 18th-century-style script on the windows, lace café-curtains, lots of dark wood and carpet-patterned chenille table-coverings.

my DH & I liked the siberie on browersgracht. not so lively but pretty relaxed with neat artwork.