From the looks of that photo, there are a few things wrong with the border:
a) The "black" is thicker on the top, and right-hand-side bar, whereas it's skinnier on the left and bottom
b) The "white border" is too thin at the top, almost half that of the bottom/sides
But since you didn't want a critique of it

, i will tell you how I would go about doing it ... it looks like a lot of steps, but it's
VERY simple and straightfoward:
0. Create a new layer, ABOVE your picture ... make sure when you crop your image, you expand the selection by 30 pixels, so you aren't cutting out any of your image (that you want) with the border

1. Use
"single row marquee" tool, select the very top and (holding down shift) select the very bottom as well2. Continue to hold down shift, and use
"single column marquee" tool on both the far left, and far right of the image. 3. You will now have a single pixel border around the entire image. Go to
Select >> Modify >> Expand .... set it to "9" and fill with black4. Press
Ctrl+Shift+I (Inverts the selection) and fill with white
5. Go to
Select >> Modify >> Contract .... set it to "20" and hit DELETEYou now have a nice looking border around your image

Sorry if it made little sense, it's much easier to explain these things in person