Here is what I did:
Cast on 36 stitches on one double pointed needle. Now divide the stitches between two more dps, giving you 12 stitches on each of three needles. Now pick up your fourth needle and join to knit in the round. (Here is a video demonstrating this technique-you may want to look for some others as well if this one isn’t clear enough for you. There are tons of knitting tutorials online. The lady in the video is using a total of five dpns, I always only use four. I find it easier and haven’t found any reason to use five.)
These legwarmers are knit with a knit 2 purl 2 ribbing all the way up. Easy.
So you will knit the first stitch, pulling it tight to avoid a gap, knit the second stitch (I always pull the second stitch tight as well) and then purl the next 2 and then just keep on with the k2 p2, round and round until you reach your desired length.
Regarding gauge, I knit these for Larkspur, although they also fit Beatrix, and I believe one of my rotten boys put them on today as well. K2P2 is very stretchy so I am not sure how important gauge really is. Your best bet is to cast on and start knitting and then after a few rounds take a look and see if they look like they are going to fit. I would say that these that I made are size 0 to 4 years, but this also depends on how skinny your kids’ legs are and of course it’s up to you how long you make them. Larkspur’s legs are about seven inches around at the thickest part of her calf, and I know my guage in stockinette stitching with this particular yarn on size 7 needles is five stitches per inch. So I just multiplied 7 x 5, and then added one stitch to make my cast on number a multiple of 4 so my k2p2 pattern would work.
When you reach your desired length (Larkspur’s are roughly 9 or so inches long, and could have been longer except I grew impatient), it’s time to bind off. Here is a good video on how to bind off ribbing on double pointed needles.
The gap will be pulled closed and you are finished. Only now you have to knit the second one. I need to learn magic loop…