How to organize the project directory structure?

Question

Software design

I am writing a web project in D. He has two parts. Server and client. There is a common code (for example, working with configs and a database). How can I organize everything in a way that avoids code duplication?
Ok, let's assume that I have classes for working with the database in separate modules. But what should the directory structure be?
server
client
modules - like to shove the common part here and refer to it or what?