I started from the train station, and tried to plan out from there. I went to all the main buildings, my character's houses, bridges, ramps, and my permanent villagers' houses. I also put a path around the outside of the plaza (but not over the whole thing). I covered most of the cobblestone bc I don't like how it looks to have a path just stop and have cobblestone start, idk. I left the train station area uncovered except for the outside edges so that if I do a trade, people have someplace to put their stuff. (I realized that after the fact

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I put unique paths around each of my character's houses and put flowers inside (sort of like their own personal gardens). As for the villagers, I put paths coming vertically from their doorways so I could put flowers on the sides of their houses as their own mini gardens.
I made all the paths two squares wide since that's how wide the bridges are (BUT NOT THE ARCHWAY PWPS DON'T GET ME STARTED). One square is just too thin imo. Makes it hard to stay on if you're running or for visitors unfamiliar with your town.
I would say to try to have an idea in mind of where you want to put them, even if you don't plan exactly. Putting down paths over your entire town can be time consuming, lol. Especially if it's the type of path that has 10 different squares.