Need help with export.php (CiviCRM 4.6 & Drupal 7)
There are a few things that can help you out:


Most importantly, the API Explorer (Support menu » Developer » API Explorer).  It will build your drush command for you through a GUI.
You can see there that adding an option with "limit=0" will return all records.
There's documentation built into the API explorer, but there's also API documentation in the Developer's Guide.
One major caveat!  drush and export.php don't really handle JSON inputs well - which you need to pass options.  Instead, use cv.
cv is like drush, but for CiviCRM.  This can take arguments similar to export.php but can also get JSON as an input, for instance:


 echo '{"options": {"limit":0}, "first_name": "Juliann"}' | cv api Contact.get --in=json --out=csv 


To use cv with the API explorer for simple commands, just use the recommended cv command.  However, if the command includes JSON, use the format above, and grab the exact JSON from the JavaScript example API Explorer generates.