The first step is cropping the image, this is very useful if you want to work with different layers or just change the background. There are several ways to crop the image, but I am going to explain only the one I prefer, using the "lasso selection tools".
When you open your file you will see a single layer in the layers tab called background, marked with a "locked" sign and italic text, this layer can't be edited with the lasso tool, you will have to duplicate that layer as shown in the pic.
Now you can delete the locked layer or leave it invisible mode by clicking the little eye, just in case that you need it again later.
Using the "Polygonal Lasso Tool" select the girl by the silhouette.
If you are working with an image high on contrast then you can use the "Magnetic Lasso Tool".
With the normal "Lasso Tool" you will get smoother edges, but the selection process will be a bit more complicated, not recommended for new users.
Once the selection process is done, go to the "Select Menu" and click on "Inverse" to invert the selection.
Now that the background is selected, you can go to the "Edit Menu" and click on "Clear".
as you can see I didn't follow the hair line, that's not necessary and could be too complicated to do with the Lasso selection tools, but you will find an easier way to do the hair part in the next steps 2
The second step is softening the image, here you can use my favorite tool: "smudge Tool". The idea is to remove the graininess and roughness of the textures by smudging with soft brushes.
First, go to the layers tab and press " Ctrl + left click" on the layer to smudge. Selecting the area is very helpful, because you won't have to worry about the edges as you can only edit the selected zone. Now click on the "Smudge Tool" and select the brush you want to use, i recommend a "medium size soft brush" for big open areas, like belly, and "tiny soft brushes" for reduced spaces like fingers.
While smudging open areas like belly, move the brush drawing soft circles, in narrow areas like arms follow the edge line direction as shown below. The strength of the brush should be under 45%. Apply short strokes, long strokes and brushes with too much strength could deform the texture, avoid that.
You can use the "Blur Tool" here too, but I don't like it because you can make some important lines go blurry, and you don't have so much control over the softening process. You can use it later over the unselected edges if they are too sharp.
In your image you will have to decide the direction of your strokes, I am only giving some tips for better results, remember to change the brush size depending on the surface shape and extension.
The third step is lighting, you will have to use several layers, other tools and the "Diffuse glow" filter in order to achieve a nice and soft lighting in your image. The first thing to do is duplicate the layers.
Select the new layer and apply the (Filter / Distort / Diffuse Glow filter), set the graininess to 1 , the glow amount depends on your image.
Now your image should look like picture 2 and your layers tab like the little box on the left. It is time to decide where do you want the light and the shadows. in this case I want the light on the right and shadows on the left, so with the glow layer selected I will use the "Eraser Tool" with a big soft brush to remove the light from the left borders as shown in picture 3.
Now you can use the "Dodge Tool" to add bright in a more accurate way. Use a little brush with low strength and apply several times until you get the desired results.At the end you can merge the normal and glow layers. Select the glow layer, go to the option "Merge down". You should get this in your layers tab:
in this step I changed the colour balance (Menu Image / Adjustments / Colour balance) increasing yellow and red. This is optional and depends on the background you are going to use. See step 4.