Drush post-installation - where can I find drushrc.php?
First off, note that alias records go in *.aliases.drushrc.php, whereas general (global) Drush settings go in drushrc.php.  You can find example.aliases.drushrc.php and example.drushrc.php in the Drush "examples" folder.  Drush will look for aliases.drushrc.php and drushrc.php in the ".drush" folder in your home directory.  On most of my systems (Linux), my home directory is /home/ga; on Linux, $HOME and ~ will expand to your home directory.  On my Windows system, my home directory is at 'c:/Users/Greg Anderson'.  To find out exactly where Drush thinks your home directory is, run:

drush ev 'print(drush_server_home());'


Create a .drush folder inside of your home directory, copy example.drushrc.php to .drush/drushrc.php, and example.aliases.drushrc.php to .drush/aliases.drushrc.php, and customize to suit.