Adjustment Layers in Photoshop.
The next time you create an adjustment layer to fix something like brightness and contrast, if the adjustment doesn't do enough just double the effect.
Here is how you do that.
Just drag the adjustment layer down to the new layer icon in the bottom of the layers palette. This doubles the effect of the adjustment layer.
If the effect is too much you can adjust the opacity of the duplicated layer to get just the effect you need.