Hey, I have a question that I'd [obviously] really love help with!

How do you make a little white border around a particular person in an icon or a header etc. Like, not a square border around the whole image... but a little white border, maybe 1 or 2 pixels wide, individually cut around a person in an icon?
I don't have an example, but I'm sure you know what I mean!

Thanks guys,
Olly X