This is a handy Drupal module that allows developers to show debugging messages on a separate page.

Here's how to use Mollom on your custom form (according to http://kahthong.com/2013/06/integrate-your-custom-drupal-forms-mollom-captcha-spam-protection)

In this example, we add the print_mail_form from the print module to Mollum's list of available forms to protect.

Make spam go away! This is a great service that is free for a low traffic site. A great anti-spam solution for Drupal! Also check out Honeypot and the Bad Behavior module.

The WYSIWYG module is my favorite for rich text editing in Drupal 6 and Drupal 7. (In Drupal 8, WYSIWYG is in core.) Here's how I set it up.

In this example, I add a template in a custom module for the print_mail_form that comes with the print module

Example of theming a checkboxes field.

Theming form elements in Drupal can be a pain. Here's how I do it.

After creating a custom form with FAPI (Drupal's Form API), it can be hard to theme it just like you want. Here's how to do some basic form theming including the creation of a template (.tpl.php) for the form. Note that the theme hook name must be the same as the form name.

The Blame module records data about each Drupal form submission.