I didn't plan my town at all when I first started. I placed everything randomly, but I didn't have any paths down at that time so it was difficult to picture where everything goes. I find it really helps to section off certain parts of your town. And you could always rub them out after a while if you want natural looking paths

My town looks pretty full now, I've got my limit of PWPs spread all over the place. Then where there is gaps I've added bamboo, fields of flowers, a small orchard and a clover and mushroom garden
It's not perfect by any means but it looks like a proper town now.
Also, planting lots of bushes has helps make it look better, they're a pain to do but I've put them along most paths and around villager houses - along with placing flowers round villager houses that colour coordinate with the villager. Just sets it off
Best of luck with your town!