You can control what goes on your issue (request) entry form to a certain extent in the queue setup, as Greg indicated. SUBJECT is a required field. The rest you were asking about are controlled in the queue setup, "NEW ISSUE FIELDS" area. Note that you may also have to work with the "Show all selected and unselected fields to" dropdown. To ensure that your users don't get all the fields you'll probably want to set that to "No Users". People can still access these fields but not from the issue entry form.