nginx and passenger to run my rails application

I'm new to Rails and trying to deploy my rails app (which runs perfectly on my computer using rails server) on to a server.

My server has nginx and passenger both installed and working fine. However, when I change the nginx config file at /opt/nginx/conf/nginx.conf as follows

....
passenger_root /usr/lib/ruby/vendor_ruby/phusion_passenger/locations.ini;
passenger_ruby /usr/bin/ruby1.9.1;
....
server {
    listen       80;
    server_name  localhost;

    #charset koi8-r;                                                                                                                                                                                    

    #access_log  logs/host.access.log  main;                                                                                                                                                            

    location / {
        root   /home/path_to_my_app/public;
        index  index.html index.htm;
    }

    passenger_enabled on;
}

it doesn't work. I'm not able to call my rails code. It keeps saying 404 error.

I restarted the nginx using service nginx restart which returned OK, but still no luck.

Can anyone tell how to debug this. Where should I check what all applications my passenger is running? What is the part I'm missing?

EDIT: I'm following this documentation very closely