You generally want to hit very fast, and hard.
To achieve this you need a good opener where you cut corners to get units out fast, before the AI starts pulling ahead around the early classical era (they start getting a ton of science at that point and will get higher military tech units out against your ancient era tech).
There are several ways to do this, but the easiest revolve around having a strong early game civ (gaul, nubia, mongolia, gran colombia etc.), or play a religious opener where you abuse crusade.
I have written extensively about the religious opener over the years, but I posted this yesterday (near the bottom with my screenshot) where I explain it a bit more:
I'm currently extending my enjoyment of Civ 6 by trying to knock out as many culture victories as possible, on Deity, in 200 Turns or less (/500 standard).
Does anybody have any favourite Civs for doing this? And any key tips for that civ? Or in general for FAST culture victories?
[I play GS, standard pace, 7 Seas, standard size (8 civs)... no extra features - HATE the extras like Secret Societies, Heroes, Monopolies, etc.]
Thus far, I've knocked out 5 victories:
1. Russia (198 turns). Lavras / Dance of the Aurora / Work Ethic - get to golden ages.
2. Canada (199 turns). Work the...
Though if you really just want to practice it the easy way, Nubia is probably the easiest.
Have 2-3 cities settled, rush archery tech and mass produce pitati archers with a few warriors.
Common for all military gameplay though is that it helps having a strong tactical sense, so that you play the terrain properly, and cycle promotions/pillages to keep units alive, cities sieged and ideally with zero unit losses.
