Step 1:
Choose your "character" photo, you are going to take the image (person, pet or anything) to mount it on another background photo, so try to get one with a solid-color background like ours. It's going to be way easy to make the whole effect.
Step 2:
Double click on your photo layer and rename it "Photo"
Step 3:
This is probably the hardest step to do, choose your Eraser Tool, and delete all the current background of your photo. Remember that you have to be very carefully and patient to get the job done well, but it's worthy, you will love the final result.
Note: This is why you need a solid iBackground color for your "character" photo; it's a lot easier to erase the background this way.
Step 4:
Choose the new background photo to make the whole montage; we have this awesome snow photo. Size is not a problem here because we are going to resize anyway.
Step 5:
Insert the "Photo" layer above your new background layer; just drag it.
Now place it in the right spot, and resize it using the Free Transform tool (Ctrl+T), this way the result is going to look natural and real.
Maybe now you will have to modify the size, angle or any other variation, for this use your Free Transform Tool again (Ctrl+T), and get just the right position.
Basically the montage is done!, to make it REAL as possible just...
Step 6:
Select your Crop tool
And crop the photo, this way your photo it's going to be pretty natural, just check the final result:
Step 7 (Optional):
If you press Ctrl+Shift+E (Merge Visible Layer) and then Ctrl+B (Color Balance), you can modify the whole result colors, play a little with the values and you will merge totally your two photos getting an awesome and easy montage.
More Tutorials: 
