Increase the number of open files limit on Ubuntu 12.04

On Ubuntu 12.04, every process could only use up to 1024 open files including socket handlers, file handlers, etc.
When we develop scalable programs, this could hinder the throughput of your programs. Many people try increasing the number, but apparently it is not straightforward.

I am listing the steps which work for me here:
(1) change /etc/security/limits.conf by adding the following lines:

your-user-name soft nofile 4096
your-user-name hard nofile 4096

(2) change /etc/pam.d/common-session* by adding the following line:

session required pam_limits.so

(3) logout and login again if you use ssh.

References

http://askubuntu.com/questions/162229/how-do-i-increase-the-open-files-limit-for-a-non-root-user