1) Create a new layer 
and using the
Rectangular Marquee draw a rectangle like fig1 below ** do not deselect it
**
Fig 1
2) While still selected, go to channel 
window and
create a new layer then fill it with white. Then go to Filter
> Blur > Gaussian Blur ..... 2px. We need to make it
smooth by go to Image > Adjust > Levels (ctrl+L), then
grab those sliders at the far ends and bring them close together (fig2), until you have a nice smooth edge
(fig3)
Fig 2
Fig 3
3) Ctrl+click that Alpha1 to load the selection then go back to
Layer window. Set your foreground color to #CCCCCC, click linear
Gradient tool, then drag from top of the selection to the bottom so it
looks like what I have in fig4 below.
Now create a new layer and dont change your foreground color and go to
Edit>Stoke for width use 1px & Location :
center. **do not deselect yet** (fig5)
Fig 4
Fig 5
4) Now, with the rectangular marquee selected move the selection up to
the top of the button so that it overlaps slightly (fig6) Then create a new layer and fill that
selection in with white.
Fig 6
5) While you still in that new layer (above)...ctrl+click the
original shape (step#3 fig4) and then go to
Select>Inverse. Hit delete and now you can deselect (ctrl+D) it.
Now go to Filter>Blur>Guassian Blur and use 1px
then set the opacity of that layer around 65% ~ 75%.
(fig7)
Fig
7
6) Click the the original shape layer (step#3 fig4) then go to
Layer>Effects>Inner shadow and use the settings shown in
fig8. That's it, you should have a nice
plastic tab (fig9) ready to add some
text.
Fig 8
Fig 9
This is what I came up with :
