Step 1
Open a document and draw a rounded rectangle. I set my rectangle radius to .5 if you were wondering.
Step 2
First, double click the layer to get to its Layer Style. Apply a gradient Overlay onto the rectangle. The gradient should be gray to a light gray color. You always want the lighter color on top. Adjust your angle accordingly. I set it to 90.
Step 3
Next, apply a 1px stroke to the rectangle. Set the color to #b1b1b1 or any semi-dark color that matches your button color.
Step 4
Now apply an Inner Glow. Set the color to white and opacity to 75%.
Step 5
Finally, apply a Bevel and Emboss. Depth should be 200%. Direction should be Up. Size to 5 and Soften to 0. Set the angle to 90 degrees as well. Change the color of the shadow mode to the same color as your stroke. Now add whatever text you want onto the button to finish it. Apply a light drop shadow onto the text and you're done.
Final Result:
