Prevent any plugin from update check. This will help if you are customizing any plugin and it will let you stop the plugin update and not loose your changes. Add this code to your plugin.

gistfile1.php

<?php
add_filter( 'http_request_args', 'my_plugin_prevent_update_check', 10, 2 );
function my_plugin_prevent_update_check( $r, $url ) {
    if ( 0 === strpos( $url, 'http://api.wordpress.org/plugins/update-check/' ) ) {
        $my_plugin = plugin_basename( __FILE__ );
        $plugins = unserialize( $r['body']['plugins'] );
        unset( $plugins->plugins[$my_plugin] );
        unset( $plugins->active[array_search( $my_plugin, $plugins->active )] );
        $r['body']['plugins'] = serialize( $plugins );
    }
    return $r;
}
?>