Open up a new document 1000px wide and 600px high. Then paste an image of a laptop into your document. Create a new layer set called ‘laptop’ and put the layer containing your laptop image into this layer set.
Now I want to create a vanishing point for the screen of the laptop. Many Photoshop users, including myself, don’t yet have Photoshop CS2 or CS3, so this tutorial won’t utilize the useful vanishing point filter available in these versions. Instead, we’re going to manually create a fake vanishing point.
Select the screen part of your laptop using the lasso tool. Then copy your selection, create a new photoshop document, and paste in the selection. Go to image>image size and double whatever your image size is. In this case the original screen was 204px wide, so I simply doubled this to 408px.
Then paste this new larger screen back into your original document. Positioning it roughly where you think it looks good in terms of perspective.
Now select your line tool and a nice bright color for it and draw lines each corner of your large screen through to the matching corner of the original screen and past to a vanishing point. Do this with each corner of the laptop screen, until you have something like the image below:
Now duplicate your larger laptop screen and select edit>free transform. Then in the menu near the top of your screen (see diagram below) change the W (width) and H (height) percentages from 100% to 90%.
Move this resized image so that it matches up with the perspective lines that you created earlier. Be sure to place this resized screen layer behind the largest screen layer but above your original laptop photo layer.
Repeat this process of duplicating/resizing/aligning using the resizing percentages of 80%, 70%, and 60% from your large screen layer. Remember that your original laptop photo is 50% of this large screen layer.
This is how your image should look after you have created this new screens and lined them up correctly: