Adjustment Layers

Here we have an image of a girl laying in the grass that needs to be edited. Now our goal in photoshop is to make this look better by using Adjustment Layers. 

First we used the Curves adjustment layer and clicked the auto button to Enhance Per Channel Contrast and Snap Neutral Midtones. Slowly we can see the color and depth come back into the image. 

Next, on top of the curves layer, we added a Levels adjustment layer. What we did with this layer is take the mid tones and made them little darker. Now we are getting some of our color back. 

Finally, on top of the curves and levels layer, we added a vibrance layer to the image. This gives all the colors richness and brightness in the image. It's up to you, the editor, to decide how much vibrance you add to the image. Just make sure you don't go overboard or the picture will look fake.