Light is very important in an image. If it is not, just try you can try these quick and easy steps in Photoshop with a couple of adjustment layers. It will work with all images.
Step 1 : I have opened this free stock image. You will find it here
It belongs to bigisbeautiful
This is how the image will look after working with the Adjustment Layers.
Step 2 : Click the New Adjustment Layer button.
Step 3 : Click on Curves from the pop up menu.
Step 4 : The Curves Adjustment Layer opens.
Step 5 : Click right in the middle of the diagonal.
Step 6 : Drag up diagonally quite high. This will brighten the image enormously overall.
Step 7 : The image has brightened a great deal. All highlights appear to have been blown.
Step 8 : Note the Mask on Curves 1 Layer. It has a tiny border around it. This means it is selected. If you don't see the border just click on the Mask to select it.
Step 9 : Press CTRL+I. The Mask changes to Black.
Step 10 : The image returns to its original look.
Step 11 : Zoom into the image with the Zoom Tool.
Step 12 : Click the Brush Tool.
Step 13 : Select a Soft Round Brush.
Step 14 : Lower the Opacity to 10% and Flow to 50% in the top panel.
Step 15 : Press x on the keyboard to switch the Foreground Color to White.
Step 16 : I have gone over with the Brush just once over the skin areas.
Not much difference is visible because the Brush is set to low Opacity.
Step 17 : Go over the skin areas, particularly the highlights four or five times painting slowly. Since the Brush and Flow are set to low values it will take some time before you can see a change.
Look at the Layer Mask. You can see the areas that you have painted away appearing faintly.
Step 18 : Press CTRL+J. A Curves 1 copy layer forms.
Step 19 : Press CTRL+I to change the Layer Mask from Black to White.
Step 20 : The image looks exceptionally bright with the highlights blown.
Step 21 : Drag the central point of the diagonal in the Curves down diagonally.
The image looks like this. Now to apply some tweaks which are very important how your image will ultimately look.
Step 22 : Click on the Curves 1 layer.
Step 23 : Click a point towards the top of the diagonal and drag gently upwards to increase the lights. Click a point towards the bottom to heighten the shadows.
Step 24 : Click on Curves 1 copy.
Step 25 : Click two points at the top and bottom and nudge it down slightly. It increases the shadows without affecting the highlights.
The finished image.
Other tutorial are here