Headers Problem

I'm getting the following error. My question is, where would I use the ob_start() and ob_end_flush() function so I can get rid of this. I have read the PHP manual, but not quite getting it.....Or if there is a better way? This is how the files work. update-corrections-input.php (user inputs info by a form). This file includes another file - restricted.inc. The form in update-corrections-input.php calls update-corrections-write.php which processes the input and then includes update-corrections-input.php again. So basically it just brings the user back to the form again. Any input is appreciated.... Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /usr/local/apache/htdocs/supreme/updates/update-corrections-write.php:2) in /usr/local/apache/php/includes/restricted.inc on line 1