First off, what is an SSK? (if you aren't a knitter, you probably shouldn't keep reading)
An SSK is a knit decrease that takes 2 knit stitches and makes them one. It is worked by slipping 2 stitches one at a time to the right hand needle and then working them together. This decrease leans to the left.
The goal of an SSK is to mirror a K2tog (knit 2 together) which is a single decrease that leans to the right.
When I first learned to SSK I was taught to slip the first stitch on my left hand needle knitwise, then the second stitch the same way and work them together:
See how much more that mirrors a K2tog? Am I a geek or what?
You can work your SSK's either way I show above, but I would say that when knitting a project you should choose one way and stick with it! Grab some needles and try it out... see what I mean?
So, how do you SSK?