Here's a simple way to generate a complete template for your bulk user CSV file.

In a 1.9 series Moodle site, log in as an administrator and find the following location on the site administration menu:

Users > Accounts > Bulk user actions.

Select a user in the "Available" column (any account will do) and click the "Add to selection" button. With this user in the "Selected" column move down the page to the "With selected users..." drop-down, select "Download" and click the "Go" button.

Next click the "Download in text format" link and save the CSV file generated.

You now have a complete CSV file ready for populating with user details (you'll still need need to add a "password" column, and don't forget to remove the details of the user you selected earlier to generate the file).

If you've added bespoke User Profile fields to your site these are also included with the correct field names.