Add a style (CSS)

1. Open \theme\standard\config.php (assume you are using "standard" theme)
2. Find the last element of $THEME->sheets (should be css3 if you have not done anything yet)
3. Open \theme\standard\style\css3.css and add your css code
4. Goto \moodledata\cache\theme\standard\css and delete all files (anyone have a better way?)
5. Done

Set up role permission

First, add this to \mod\your_module\db\access.php (after line $capabilities = array( )

    'mod/your_module:view' => array(
        'captype' => 'read',
        'contextlevel' => CONTEXT_MODULE,
        'legacy' => array(
            'teacher' => CAP_ALLOW
        )
    )

Open \mod\your_module\lang\en\your_module.php, add this line:
$string['your_module:view'] = 'View your module';

Change version.php to new version, and then goto Notification.

Use this to test the permission:

$context = get_context_instance(CONTEXT_MODULE, $cm->id);
has_capability('mod/your_module:view', $context)

Construct a url string

new moodle_url( 'url_path', array( 'paramenter1'=>$value1 ) );

Make new module with groupING

In mod_form.php, add this line:
$this->_features->groupings = true;

Note: But i still wonder why others module don't add this line but they are still available for groupING, any idea?

Add a table to Module Database

1. Site administration -> Development -> XMLDB editor
2. Find your module and click [Load]
3. Click [Edit]
4. Click [New table] and fill in the detail
5. Click [Back]
6. Click [View PHP code]
7. Select action: create table
8. Select table: select your table name
9. Click "View"
10. Copy the code to mod/your_mod/db/upgrade.php
11. Change XXXXXXXXXX to new version number (e.g. 2011022301)
12. Open mod/your_mod/version.php, change $module->version to the new version number
13. Notification 
14. Done

Create a new format

1. Goto course/format/ (read the README.txt there)
2. Copy topics folder to a new folder (e.g. yourformat)
3. Goto yourformat/lang/en/
4. Rename "format_topics.php" to "format_yourformat.php"
5. Open format_yourformat.php
6. Change the $string
7. Done.

Note: course/format/yourformat/format.php is the file for output view

Add new field to user profile

Site administration -> Users -> Accounts -> User profile fields