Step One:

Open image in Photoshop.

Step Two:

Correct the image using your normal workflow. Correct levels, curves, color, shadow/highlight, sharpness, etc.

Step Three:

Make a copy of your image that includes all of your adjustments on a new layer. Do this by making a new layer on top of your adjustments and then, while holding the ALT key, go to merge visible. This will make a copy of all visible layers into one "new" layer.

Step Four:

On a new layer, create a frame or object that you can use to demonstrate the 3D effect.

Step Five:

Add a layer mask to the frame layer.

Step Six:

Using a black brush, brush to reveal the areas that you want to appear on top of the frame. Remember you can always switch back to white and undo areas that you did not want to reveal.

Step Seven:

After you are satisfied with the mask, add a slight gaussian blur to smooth out the selection.

Step Eight:

You can use the frame as-is as just an added element to the picture, or you can erase the parts of the image that you do not want to keep. With this picture, I am erasing all but what is in the frame, the hand and the disk. I have also added a white background under the image layer so I can more clearly see as I erase.

Step Nine:

Once you have your cut-out, you can copy it into other images etc. The sky is the limit. Use your imagination and have fun.

Sometimes it is good to just make a very subtle effect such as Img#2 below. But, as you can see from the collages below, you can really make that ho-hum picture or colloage into something unique.