Example of how to add attribute to customer entity type in Magento

mysql4-install-0.1.0.php

<?php
$installer = $this;
$installer->startSetup();
$installer->addAttribute('customer', 'civility', array(
    'label'        => 'Civility',
    'visible'      => true,
    'required'     => false,
    'type'         => 'int',
    'input'        => 'select',
    'user_defined' => '1',
    'source'       => 'eav/entity_attribute_source_table',
));

$tableOptions = $installer->getTable('eav_attribute_option');
$tableOptionValues = $installer->getTable('eav_attribute_option_value');
$attributeId = (int) $installer->getAttribute('customer', 'civility', 'attribute_id');

foreach (array('Mr', 'Mrs', 'Miss') as $sortOrder => $label) {
    $data = array(
        'attribute_id' => $attributeId,
        'sort_order'   => $sortOrder,
    );
    $installer->getConnection()->insert($tableOptions, $data);
    $optionId = (int) $installer->getConnection()->lastInsertId($tableOptions, 'option_id');
    $data = array(
        'option_id' => $optionId,
        'store_id'  => 0,
        'value'     => $label,
    );
    $installer->getConnection()->insert($tableOptionValues, $data);

}

$installer->endSetup();