I'm constantly telling producers that they need to improve their stock photography. Too often it's poor quality, low resolution and plain boring. If you can afford a professional photographer - do - it's not an area to skimp. If that's just not an option, there are some tips available. Paul Dymond's blog http://pauldymond.blogspot.com/ has lots of great suggestions in an easy to digest format. It's essential reading.
Photographer and foodie Gordon Hammond also has some great tips in his latest newsletter http://www.australianregionalfoodguide.com.au/
If you want to brush up on your skills, Blue Dog http://www.blue-dog.com.au/runs regular courses that will help.