Create your self-signed certificate:

openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 3650 -nodes

Configure your nginx:

server {
    listen 443 ssl;
    listen [::]:443 ssl ipv6only=on;

    # Diffie-Hellman parameter for DHE ciphersuites, recommended 2048 bits
    ssl_dhparam /etc/nginx/ssl/dhparam.pem;

    # enables server-side protection from BEAST attacks
    # http://blog.ivanristic.com/2013/09/is-beast-still-a-threat.html
    ssl_prefer_server_ciphers on;

    # disable SSLv3(enabled by default since nginx 0.8.19) since it's less secure then TLS http://en.wikipedia.org/wiki/Secure_Sockets_Layer#SSL_3.0
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

    # ciphers chosen for forward secrecy and compatibility
    # http://blog.ivanristic.com/2013/08/configuring-apache-nginx-and-openssl-for-forward-secrecy.html
    ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:ECDHE-RSA-RC4-SHA:ECDHE-ECDSA-RC4-SHA:RC4-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!3DES:!MD5:!PSK';

    # config to enable HSTS(HTTP Strict Transport Security) https://developer.mozilla.org/en-US/docs/Security/HTTP_Strict_Transport_Security
    # to avoid ssl stripping https://en.wikipedia.org/wiki/SSL_stripping#SSL_stripping
    add_header Strict-Transport-Security "max-age=31536000; includeSubdomains;";

    ssl on;
    ssl_certificate /etc/nginx/ssl/cert.pem;
    ssl_certificate_key /etc/nginx/ssl/key.pem;

    server_name DOMAIN.com;

    root /usr/share/nginx/html;
    index index.html index.htm;

    client_max_body_size 10G;

    location / {
        proxy_pass http://localhost:2368;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_buffering off;
    }
}

# redirect all http traffic to https
server {
  listen 80;
  server_name .DOMAIN.com;
  rewrite ^ https://$host$request_uri permanent;
}

Restart nginx:

service nginx restart

Cloudflare also publishes what they consider up to date, secure ssl cipher settings.