I had trouble installing Drush on my newly created Centos box. Therefore, I have documented my steps.
First, you need install Composer ( PHP Dependency Manager) cd into the
$ cd /tmp
Download Composer.phar here
$ curl -sS https://getcomposer.org/installer | php
Then move it to /usr/local/bin so that it can be used globaly.
$ mv composer.phar /usr/local/bin/composer
Now type $composer
If you done everything right you should get something that look like this: