1. Open a "scenery" photo in Photoshop
2. Use File > Place to insert a new photo (Portraits work best)
3. Set the new layer's Blending Option to Screen or Lighten - Screen leaves more white - Lighten removes more of the portrait image
4. Right click and rasterize the layers and convert to black and white (Image > Adjustments > Black & White) for cleaner color
5. Fill the portrait background in with white or delete it for a cleaner look
6. You can also delete parts of the portrait for a "blended" look (Deleted parts will show the background image through)
7. Move the photos around to create a "blended" effect
8. Flatten layers and edit levels