First of we want to create a new document - Sizing 164 x 50 This is totaly up to you.
First Step, We will create a rounded rectangle, fill this rectangle with the colour you'd like your bar to be. I will be using black which is #000000 (Enter this in the Colour Area) - Set the radius to 5px on the top toolbar.
We should now, have something like this.
Now, we will apply the following styles.
Adding - Outer Glow
Adding - Stroke
Now we will create an rounded rectangle, with the radius of 5px. This one will be the reflection shape, so it is going to be positioned at the top, also it will be smaller. I used White for the colour of this shape.
Now, click the Add to vector mask button on the bottom of the layers palette.
Now, change the foreground and background to White and Black, so we can create a gradient. Right Click the layer, and click Gradient Overlay.
Now it's time to add text to our Button. Add what ever text you like, the rest is self explainitory.
PSD File, Can Be Downloaded Via PMing Me.