Alright, first things first, let's get that user authentication system up and running. You can use built-in features or go with third-party options like Firebase, Auth0, or AWS Cognito. They're all pretty solid choices.

Now that you've got authentication sorted, it's super important to store those session tokens (like JWTs) securely. The best place for these is in HTTP-only cookies. They're much safer from XSS attacks. Avoid using localStorage for anything sensitive.

Next up, let's set up some middleware to handle user sessions. This middleware should check for a valid session token with each request. If the token's good, let 'em in. If not, send them back to the login page.

Make sure your system can handle token expiration properly. You don't want users getting kicked out unexpectedly. Implement token refresh logic so users can stay logged in without having to re-enter their credentials. You can use refresh tokens or short-lived tokens with a refresh endpoint for this.

Don't forget to give users a way to log out. When they do, make sure to clear any stored tokens and redirect them to the appropriate page.

Keep an eye on active user sessions. This helps you spot any unusual activity and manage session limits. Log session creation, last active time, and associated IPs to keep track of everything.

Make sure only authenticated users can access certain routes. Protect these routes by checking the session token and verifying its authenticity before serving any restricted resources.

Allow users to stay logged in across multiple devices. To do this, ensure your session management system can handle multiple active tokens for a single user account. Also, provide ways to manage these sessions, like session revocation for lost devices.

Finally, regularly review and update your session management logic. Make sure it complies with the latest security standards and practices. This includes updating libraries, reviewing token handling, and monitoring for XSS or CSRF vulnerabilities.