Produce looks better against a white background than a black background in my opinion. White looks fresh and clean, and fortunately, most produce shows up well against white. It also doesn't hurt to shine it up a bit.
To create the white background:
I did pretty much the exact opposite as what I did in my Instructable for creating a perfectly black background. I placed a piece of white poster board in full, harsh sunlight so that it was uniformly bright which meant angling it towards the sun against a step ladder. Then I held (or had my significant-other/upside-down-beer-glass hold) the tomato in the shade. The shade is nice and soft but still pretty bright. However, the poster board absolutely glows in comparison. The goal is to get the background uniformly brighter than the subject. You can easily get more creative with lighting and produce some better shots, but this is INCREDIBLY easy to do and requires only one light source - the sun.
To create the wet effect/shine:
I used olive oil. I've tried photographing shine/wet using water, and it really doesn't work well. Water evaporates very quickly, and it doesn't have the same "hold" as oil does. I first washed the tomato (picked fresh from the vine today!) and rubbed it down with olive oil, and a few of the shots are just with that shine alone. However, I wanted it to look wet, so I pipetted some extra oil around the top and let it drip as it pleased.
To add context:
I played with a variety of hand positions. When I held the tomato in the palm of my hand, the tomato looked bigger. When my significant other held it in the palm of his hand, it looked smaller - he was nice enough to muddy up his hands for a "fresh out of the garden, Farmer Brown" look. I also played with how my fingers were arranged, and I also propped it on an upside-down beer glass just in case the absence of hands made it a little more appealing. Minor details start to REALLY matter when the shot is minimal. Finally, when I had the shots I liked, I took a bite to see if the "fresh bite" look helped, but it didn't. All I could after that point was continue eating.
This process is not limited to photographing produce. It can be used for a variety of other subjects.
Bon appetit and happy photographing!