So, you have decided on the photo where you want to create the effect of long hair. Open it in Photoshop: File (File) - "Open" (Open).
Select the Lasso tool/Lasso Tool (L). Feather put it in the range of 9-12 pixels.
Circle the part of the hair that you want to lengthen, the Lasso tool.
Copy the selection to a new layer: menu "Layer"/Layer - select "New"/New - command "copy to new layer/Layer via Copy (or press Ctrl+J).
In the palette "Layers" icon will appear in the new layer.
Click the menu item "Edit/Edit "Free transform/Free Transform (or Ctrl+T).
Now click inside the frame transformation, right-click and select Distort. (Although, if the hair is straight and smooth, one can do a free transform, no distortion).
Lengthen the hair or modify the hair, moving the squares on the frame transformation.
Similarly do with the other side of the hair highlighting part hair and creating a new layer. For variety, you can use the command "Edit/Edit - Transform/Transform - Warp"/Warp (or just select instead of "Distortion" item "Deformation"). This method allows you to configure the parameters of the hairstyle.
Hair can be modified, again moving the squares on the grid transformation.
Hairstyle is ready, but there is a defect of a light halo at the bottom of the hair. This undesirable effect was the result of a transformation, when a part of the background has been involved on the hair. This defect must be eliminated.
Click on the third from the left icon in the palette "Layers". On the top layer will appear a white layer. The image (picture) will change.
Select the Brush tool/Brush Tool (B).
Menu the Brush tool (at the top of the screen, just below the main menu) set the zero rigidity, and also select the brush size.
Also make sure to set the black foreground color.
Then circle the brush light halo and to tweak the resulting hairstyle. Now click on the second layer to work in it, and do the same on the other side. Your new hairstyle is ready.
In addition, you can apply any special effect to your photo.