When building up a new Drupal 6 site now, we always download and enable the following modules to enable WYSIWYG (What You See Is What You Get) edition:
- wysiwyg
- we download the ckeditor sources
- imce
- imce_wysiwyg
- enable wysiwyg, imce and imce_wysiwyg
- put the ckeditor sources in sites/all/libraries/ckeditor (ckeditor.js must be callable as /sites/all/libraries/ckeditor/ckeditor.js)
- fix (if needed) the wysiwyg module to detect ckeditor version 3.6 (see http://drupal.org/node/1143104)
- go into imce configuration and check where to put the files (the default directory is OK for small sites)
- go to wysiwyg profiles definition, select ckeditor for Full HTML profile
- save and edit the Full HTML profile
- check a few boxes in the "buttons" section, *including* IMCE
- change the CSS to default editor CSS (otherwise sometimes you won't see a thing when you're editing)
- save