This page gives a short list of things to be aware of when developing Drupal modules.
Use tools to evaluate your module’s pages for accessibility
Use the Web Accessibility Evaluation Tool (WAVE) toolbar or another automated tool to check any pages or blocks that your module creates for accessibility issues.
Here is a list of more accessibility validation tools. These tools will not detect all accessibility problems, but are a great start.
Use the Form API appropriately
If you use the Drupal Form API, it will do a lot of work towards making your forms accessible. Make sure when using hook_form_alter and other techniques to modify forms that you are not reducing the accessibility of forms.
Use #title and #description
Every FAPI element should have the #title property set. This makes a label for the input field so that screenreader users know what the input field is for. The #title property should indicate the label associated to the form element. It should not be used for formatting other text (to create a heading, for example).
If the form element needs additional description beyond the title, set the #description property as well.
$form['pass'] = array(
'#type' => 'password',