Comment by jacquesm

In "distinción" spanish, the classic pair is the word for house and for hunt - "casa" and "caza" respectively. If you pronounce them the same (with an S sound), you're a Seseo speaker like (most) latin america. If you pronounce them with different sounds, one an S sound, the other a TH sound, you're a "distinción" speaker, and if you pronounce them both with a TH sound, it's the more uncommon ceceo accent, usually largely Andalusian.

Any c+e/i (cena, cine) or z+a/o/u (zarza, zorro, zurrar) is a good heuristic.

c+a/o/u sounds like k (casa, cosa, cuchara) and z+e/i does not exist.

My favourite word to troll people who are learning the language is "cerrojo" /θe'roxo/, meaning "latch" or "lock", as it contains the three most difficult consonants in the language in sequence xD

cien