Knit stich -- increasing w/out hole??

Quick question for the knitters...

I'm trying to make a ruffle to DD's soaker capris and for the life of me I cannot remember how to increase without getting a hole.

I thought knitting one stitch twice would do it -- once in the front as if to knit and once in the back as if to purl -- but I still ended up w/ very visible holes.

Anyone able to describe it or have a link to something I can look at???

Thanks!!

~Erin