Here's a step-by-step of my favorite decrease. It pulls both sides together towards a central raised stitch, which looks pretty great. It's featured heavily in the squid pattern.
Step one: slip two stitches together as if to knit:
Step two: enter next stitch after the 2 you just slipped ...
... and knit it
Step three: With the left-hand needle, enter the two slipped stitches and pass them together over the stitch just knit.