Here are the steps:
Step 1: Set #9F9F9F color as the forground color and with the help of Ellipse tool draw a circle.
Step 2: Press Ctrl+J to duplicate the layer, then right click on its layer name in layer palate. Now, select the blending options >> Choose Gradient Overlay and give the values as shown in the below figure.
Step 3: Add a 2 pixel wide stroke in it with #F0A71F color. Now, your image should look like this:
Step 4: Change the foreground color to #40080F. Now, select Rounded Rectangle tool to draw an elliptical shape twice the size that you want the smile to be. Now, Right click on its name in layer palate and select Rasterize layer.
Step 5: Remove upper portion of the shape and add 2 pixel stroke colored #FFA53F .
Step 6: Place it as shown below.
Step 7: Press Ctrl+J to duplicate the layer. Fill it with gradient overlay and give the below values.
Output should look like this:
Step 8: Now, use the eraser tool to erase part of the image.
Select high feathered brush and press it once in the middle of the shape. Use white color for that.
Step 9: Draw this shape with the help of Rectangle tool. You can find this tool in the toolbar.
Step 10: Apply the below gradient setting for filling the shape.
Step 11: Rasterize the layer and erase the left portion of the rectangle to have a shape like below.
Step 12: Now, Change the foreground color to #3F678F and draw a small circle with the help of ellipse tool.
Step 13: Duplicate this and place it as shown in the below figure.
Step 14: Using brush tool, draw a white line as shown in the figure.
Step 15: Final step is to add little shadow below the image by selecting gray color and draw with the help of brush tool. Your smiley is ready now :-)