You can spot the reporter when he or she whips out a notepad after entering the open business and loooking around for a bit and starts scribbling notes on it.
Talking, joking or otherwise positively interacting with the reporter as early as possible will help garner a good review.
There's also a hack here which inlcudes a 'spawn reporter' option:
http://modthesims2.com/download.php?t=136990