It is important to knit at a gauge tighter than what you would normally use for the yarn you choose. For example, if you are using a worsted weight yarn, try a 4US instead of a 6US or 7US.

I have knit this in anything from a DK single to a worsted held double. The important thing is to use a smaller needle than what you would normally use. The tighter the fabric the wavier the waves.