Step 1:  Create a 200px by 100px blank document and fill the background layer with white. Create a blank transparent layer on top and select it. Then, using the rectangular marquee tool / Elliptical marquee tool, or shape tools, design an oval shape filled with black as in the figure to the left. After this is done, go to the layers palette and set the Fill to 0%.

Step 2: The oval should disappear, but it'll be back soon. With the pill button layer still selected in the layers palette, click on Layer > Layer Style > Drop Shadow in the menu and duplicate the settings on the left. You can, of course, alter the settings to your own personal taste later, but DON'T exit the layer style dialogs until the end of step 6.

Step 3:  Now progress onto the inner glow subsection and enter the settings shown here. This will add a dark outline to the pill button and solidify its presence.  After all, if the button were near totally transparent it would be an absolute nightmare to find!

Step 4: This is where most of the magic happens!   Go to the Bevel and Emboss settings and enter the settings on the left.   The gloss contour applied is not included as default with Photoshop, so click on the curve itself and create a duplicate of mine. Don't get too obsessive trying to produce an exact match - its not that critical.

Optional:  If you want to change the look of your glass, this is one of the main places to do it. The Depth setting can be varied to sharpen or soften the lighting by increasing and decreasing the value. Likewise, playing around with the gloss contour can help tighten effects around curves, or make them appear softer. Finally, increasing the size and soften settings can make the glass appear smoother or shinier, but only up to a point - overdo it and you'll end up with something that looks daft!

Step 5: Now progress onto the contour subsection and alter the curve into the one on the left (again, its a custom one not included with Photoshop). You can try playing around with this setting if you like, but the effects are unpredictable and best left alone.

Step 6: For our final step, go to the satin section and enter these settings. This will re-create a light diffraction effect within the glass, and is rather essential if you are aiming for a more realistic effect. The contour this time is, thankfully, included with Photoshop as standard and named 'Cone - Inverted'.

Step 7: Now press OK to exit the layer effects dialog and admire your work! You can, of course, give the glass a coloured tint with the Colour Overlay functionality of layer effects or even a texture with the Texture Overlay feature, but I'll leave the experimentation up to you...

Variations: As expected, the glass pill is transparent. To maintain a realistic glass effect you should, of course, apply a Gaussian blur or displacement effect to all layers underneath the pill to simulate differing optical densities.