I had this problem with my town map too when I started a second town because I didn't like my first one. I recommend looking around some dream towns to get some inspiration.
I agree with Melyora except for one thing. In my opinion you don't need to worry about is villagers and their placement because that can always be changed. You can wait for them to move out (or not if you're a time traveller) and there's always villager plot resetting when the new ones move it.
There's a lot of aspects to think about when thinking of your town layout.

For example, the river shape, whether you want the ocean to run up the left or right hand side of the map, whether you want the secret beach or not etc. It's a good idea to think about your landscaping, will you want winding paths that take up a lot of spaces? PWP near water? Do you want your mayors house is a specific place? I actually got the idea for mine from another dream address I visited and I have no idea I wanted it until I saw it. I have the river at almost an upside down U shape and my mayors house sits up at the top of the U, with lots of trees, bamboo, flowers and bushes lining the sides of the U, which I love the look of.
Also, one of the things that annoyed me, was that the colours of the train station and town hall interiors changed everytime I started a new town, this cannot be changed. You can always change the exterior but I hate the brown colour of my train station so that's another thing I would commend you think about if you want.
Hope this helps, if you have any questions feel free to ask.