As requested, here a few tips for making adjustments on the computer.
I feel I should point out that your goal in correcting throwdown entry photos should be accuracy, not enhancement. You want your food to look as good in the photo as it does in reality -- not better.
I use Photoshop CS5, but Photoshop Elements does everything you need to do to post good food shots on the forum. Other programs may do the same stuff, but I don't know those programs. Depending on the version of Photoshop or Elements you use, the menus may differ from what I post below. These should be good for most versions, though.
There are many good video tutorials on YouTube covering all of the controls I mention. There is no way I can teach you how to use all of these controls in this thread better than these videos can. I am mainly telling you which windows and commands in Photoshop and Elements I would use.
1. All digital images, even the ones from my professional Nikon D3, need some amount of sharpening. In Photoshop, I use Filter>Sharpen>Smart Sharpen. You will need to experiment with settings to fit your camera. For my D3, I set the Amount at about 120 (for full-size, 300 DPI images), and the Radius at 0.6, and adjust for Gaussian Blur, in most cases. With smaller, lower resolution images, that Amount will be too much. You just need to experiment. Once you get it right, you can apply that to all your images from one particular camera.
2. For color and contrast corrections, I have found that the Image>Adjustments>Auto Levels command often does a decent enough job for a lot of images, if you don't want to mess with manually adjusting your levels. The Image>Adjustments>Levels control window will give better results than the Image>Adjustments>Brightness/Contrast control window. So, I would choose Levels over Brightness/Contrast every time.
Auto Levels will do some color correction, too, as it tries to make what it thinks is absolute white look absolutely white. Using the eye droppers in the Levels controls window will do some color correcting, too. If you shoot under good lighting, like daylight, that alone may be all you need to do to get good color.
Image>Adjustments>Auto Color will give you a better results, especially for shots taken in tricky lighting. If you want to go manual, use the Image>Adjustment>Color Balance controls. The Image>Adjustments>Hue/Saturation controls are NOT a good way to adjust color. I also use Image>Adjustments>Selective Color from time to time, when want to enhance one color.
If your colors are weak, which often happens if your images are also low contrast, use the Image>Adjustments>Hue/Saturation controls ONLY to adjust the color saturation. Ignore the Hue and Lightness sliders -- those jobs are done better with the Color Balance and Levels controls. You can also use the SPONGE tool to adjust the saturation up or down on just certain parts of your image. So, if your tomatoes are weak, but everything else is good, you can punch up the color of the tomatoes. Of course, for a throwdown, you need to be careful not to make your foods look better than they really look. Use good judgement when you do any selective tweaking.
That's what comes to mind right now. Perhaps other Photoshop users will have some more tips, and people who use other programs can help translate. Ask questions if you have them, but the best way to learn this stuff is to do it. Watch some YouTube tutorials, and practice.
CD