This is the method I've been using for about a year now. I came up with it myself but based it from what I was seeing all over the internet. There are many similar methods and some really good ones (check out the tutorial from moonwitch).
Ok, here we go.
1. Make a new file with a size of 400x400.
2. Make a new layer.

3. Create a circle with the elliptical marquee tool. (Hold down shift to make a perfect circle)
4. Fill the circle with a color of your choice. I used #336699.

5. With the circle still selected, make a new layer.
6. Fill it with a gradient that goes from white to transparent.


7. Use the marquee tool to make an oval at the top of the circle.
8. Invert the oval selection (control-shift-I).
9. Delete the selection.

10. Select the area around the main cirlce (probably layer 1) and expand (Select > Modify > Expand) it by 3 pixels, make sure you select the gradient layer (probably layer 2) then delete.

11. Blur the gradient layer by 3 pixels.
12. Now go into the blending options and add a black inner glow, a black outer glow, and a semi-transparent gradient overlay. I'll leave these settings up to you because it's mostly personal preference.
So there we have it!

I hoped you enjoyed this. You can also use a similar method with other shapes to create that reflective effect.

