If we're talking about Toshikazu Kawaguchi's series, I usually just go publication order: 'Before the Coffee Gets Cold', 'Tales from the Cafe', 'Before Your Memory Fades', and then 'Before We Say Goodbye'. That's how they came out in English. Makes sense because the cafe's rules get established first, and the later books build on that foundation and occasionally weave threads between characters from different volumes.
A friend tried reading 'Tales from the Cafe' first because they found it at a library sale, and they said it was fine, but they missed some of the emotional payoff from seeing characters like the novelist or the sisters get their full arcs later. The stories are mostly self-contained, but the atmosphere and the cafe's lore build cumulatively.
I've seen some fan wikis list a chronological order based on the characters' timelines, which is a headache I wouldn't recommend. The publication order has a gentle rhythm to it, like visiting the same quiet cafe over a few years.