Photoshop your head onto a bodybuilder

Steps

1. Use a camera to take your picture. Try to get the shadows on your face to match the shadows on the face of the bodybuilder
2. Copy and paste your head into the photo
3. Resize the photo so it is close to the size of the bodybuilder. Drop the opacity to help see underneath.
4. Turn off the eye on the top layer then use the cloning tool to delete the original persons head.
5. Create a layer mask (small button at bottom of layers palette)
6. Use a regular paint brush to delete the back of your head
7. Go to image adjustments and exposure to lighten or darken your head to match the skin tone of the person
8. Image>adjustments>color balance to match color