This is my source pic, i label it as S.
This is my handsome pic, i label it as O:
First, i cut and paste my picture into the S picture. Turn low the opacity and fill and adjust the position so that it fit the S picture:
Erase the unwanted area.
Go to image-adjustment-brightness and contrast and adjust the lightning.
Go to image-adjustment-color balance and adjust the color of O picture until you get harmonic tone.
Repeat these steps until you get the desired colour.
Mine look like this:
Repeat all these steps until you get the best result. By combining dodge tool and Smudge tool, you can adjust the edge of O so that it looks like real. Here's mine:
Now you can look at your "new" hairstyle and see if it suit you or not before going to saloon.
If you want to make it look real, repeat the steps mentioned above.
Well, it took time but i guaranteed you will master it in a short time.
This is the one that i do very careful adjusting the brightness and contrast, colour balance and hue and saturation for both pictures. Here's the result..
Good Luck...