pixel paint
One of the many things we (Dave and I) learned at Bert Monroy's session at Photoshop World was that we should never assume! If there's any doubt about what something should look like just try it out!

Below you'll find our study on reflections. In every example that I've posted the: actual photo is on the left and on the right we follow the standard tutorial advise - duplicate the image, flip it vertically and lower.

Because reflections exist in the real world and always have, none of this should be new to anyone.

side by side comparison of real reflections and those created in photoshop

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ABOVE: The laptop is propped up about 1 inch for this shot so that the keyboard was clearly visible. Notice that in the actual photo, which is on the left, none of the keyboard is visible in the reflection.
side by side comparison of real reflections and those created in photoshop

Click the image for a larger view.

ABOVE: The next set up is a cup and saucer with a spoon resting on the saucer. Comparing the two side by side you'll notice that only the bottom of the saucer and part of the spoon handle are visible in the real reflection (left). Also notice how the real reflection diminishes in size as it gets closer to the camera/viewer. This is because reflections also adhere to the rules of perspective.
side by side comparison of real reflections and those created in photoshop

Click the image for a larger view.

ABOVE: Here you'll find two different attempts made in photoshop displayed on the right. In the first we flip the image, line it up and leave it. In the second we flip the image and snug it under the cup and saucer. Neither one really does the trick though. Also please notice how the real reflection (left) has its own glints, highlights and shadows independent of anything that can be referenced on the actual cup and saucer.
letters photographed over a reflective surface

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ABOVE: For this photo we used magnetic letters and a carpenter's square to hold them vertically over the plexiglass. The reflection created shows the slight inward angle of the letters. This is one time when the typical photoshop tutorial will work! Oddly enough most of the tutorials dealing with text will try to spice up the boring reflection with strange perspective pulls and stretches -go figure.
I hope you've found this to be helpful. I will gladly add to this if there's anything specific you'd like to see, just give let me know.