Surrealism Magritte style - part 1

Remove the background:
Use the eyedropper to pick the background color, go to select>color range

(There is a great video tutorial on PST with all the steps.
Go to the "Chroma keying" tutorial if you want to learn more)

Look for a nice blue sky with white clouds, like you see in many Magritte paintings.
Copy the background and make the sky softer by changing the brightness.
layer>new adjustment layer>brightness/contrast
Then add the layer of the portrait.

Look for a shape you want to play with. Magritte often used a bird, in this tutorial I am using an apple.
Remove the background (here it's very easy, you can use the magnetic lasso tool because the contours are very clear) and paste the apple on the face.
Make sure the highlight is on the apple layer. Now, use the magnetic lasso again and we can go to step 4.

Make sure the dotted line around the apple stays there.
Now highlight the layer of the girl.(click on that layer in the layer window with your mouse)
All the layers are still visible (you can see that because each layer in the layer window has an eye on the left, that eye indicates the layer visibility)

Click on the eye of the apple layer. The eye is gone, and so is the apple. The dotted line is still there.
This will make it easy to erase the part of the face where the apple should be.