Do you adjust the levels on your camera or on photoshop or a program afterwards?
It's a mix of both. I use a camera that takes both JPEG and CR2 formats, the latter of which captures a great deal more image data than a jpeg. I also bracket a lot, which means I tend to take a dozen or more pictures of each pose with different brightness settings. Once they're all in the computer, I pick the best one and tweak that. Up until recently I was using Photoshop, because that's what I was familiar with from work, but recently switched to Adobe Lightroom, which has a lot more photo-specific development settings that allow for a great deal of control.
The advantage of digital over film, especially in a controlled setting at home taking pics of toys, is you can take a bajillion pictures with all different settings then weed out the handful of great ones.
If you don't have access to Lightroom, Photoshop can do many of the same things, and in a non-destructive way (just don't write over the original image file). Exposure, Levels, Brightness/Contrast, Hue/Saturation, etc. You can even get into filters like Sharpen, but those require a light touch.
I totally encourage messing around. Take some pictures and just try things out! I'm no professional, but my pictures definitely benefited from a lot of practice and trial and error.