Ruching - Garter Stitch Stripe. Easy to follow and easy to remember. The pattern is so fun to come up with unique combinations of yarn and color.

Cast on any number of sts.
Knit 8 rows (4 garter stitch ridges).
Increase Row: (RS) Knit into the front and back of each stitch, doubling the number of sts.
Knit 12 rows in stockinette (knit on right side, purl on wrong side).
Decrease Row: (RS) Knit 2 sts together across, decreasing the number of sts by half.
Continue alternating these two motifs until the desired length is achieved. End with 8 rows of garter stitch