This video knitting tutorial will help you learn how to knit the center double decrease. This technique decreases two stitches at once and creates a prominent center stitch at the decrease point.
Step 1: Insert your working needle through the first two stitches on your main needle knit wise, and slip them off together.
Step 2: Knit the next stitch on your main needle.
Step 3: Pass both slipped stitches together on your working needle, over the stitch you just knit.