Building a social network begins with the crucial step of user registration, which involves setting up a backend using Node.js and Express.js, with modules like Couchbase Node.js SDK/N1QL, body-parser, uuid, and node-forge. The process involves creating a comprehensive file structure for the application, including key files such as app.js for setup, routes/routes.js for defining API endpoints, and models/usermodel.js for handling user data. The '/api/registerUser' endpoint processes user registration by validating user information such as name, email, and password both on the front-end and back-end to ensure security and prevent manipulation. Successful registrations are stored as JSON documents with unique identifiers (UUIDs), and further secured with hashed passwords. The document structure is designed for flexibility and efficiency in querying, using Couchbase’s N1QL language. Additionally, user email verification is a recommended step, to be discussed in subsequent posts.