How to add a border in Photoshop CS5

Adding a border is one of the most common things people ask me. Everybody wants to add borders and although the process is simple, it's a tricky thing to work out and not many people understand it.
Here are a few simple steps

First you'll need to set your two colours to the colour you want the border, as you can see i've done here

Then go to Image > Canvas size

you will see this window

INCREASE the two top amounts by 0.5 as shown below

Press enter and your border will filler with the colour you chose at the start!!