Subscribing on events in Magento custom models

To subscribe on events only for your custom models in Magento you need to redefine $_eventPrefix property of your model like this:

<?php

class Vendor_Module_Model_Something extends Mage_Core_Model_Abstract
{
    protected $_eventPrefix = 'custom_event_prefix';
    
    ...
}

Then you can subscribe on your events in etc/config.xml file of your module as usual:

<?xml version="1.0"?>
<config>
    
    ...

    <global>

    ...

        <events>
            <custom_event_prefix_save_after>
                <observers>
                    <your_identifier>
                        <class>Vendor_Module_Model_Observer</class>
                        <method>yourMethodName</method>
                    </your_identifier>
                </observers>
            </custom_event_prefix_save_after>
        </events>
        
    ...

    </global>

...

</config>

What model events are available?

Here is a list of available events for a model in Magento 1.9 (assuming PREFIX will be replaced by your prefix):

PREFIX_load_before
PREFIX_load_after
PREFIX_save_commit_after
PREFIX_save_before
PREFIX_save_after
PREFIX_delete_before
PREFIX_delete_after
PREFIX_delete_commit_after
PREFIX_clear

Explanation of some:

Other events are pretty obvious.

What about standard models?

Magento standard models already have their own event prefixes. If you need them, just do a search for $_eventPrefix = in app/code/core/Mage folder.