help with modifying edit forms

Hi,

I'm trying to find info on how to programmatically modify CCK node edit forms. I've looked here[1] a little, but that's D5 & I'm on 6, so I'm not sure what to believe. I see something about "form_elements" here[2], but it's not detailed enough for me to understand how to make use of it. I've also tried just hacking around with form_alter to no avail. Is there any current, clear documentation on this sort of thing?

[1] http://drupal.org/node/101742
[2] http://drupal.org/node/177892