Choose 2 circular needles of the same needle size. The cable length need not be the same, but the tips need to be the same size. Unlike with double-pointed needles where the needles rotate around the work, with 2 circs you will always knit the same half of the work with the same needles.
If knitting 2-at-a-time socks, make sure you have a long enough cable to accommodate the stitches. This tutorial demonstrates knitting one item at a time (i.e. a sock or a sleeve)
Note - if your gauge noticeably changes when knitting with needles of different materials, try not to mix needles. For the photo tutorial, I have used 2 different needles so it is easy to distinguish between the 2 needles as I describe the steps.
Cast on all of your stitches to one of the circular needles. For our purposes, the metal needle is Needle 1 (N1) and the green wooden needle is Needle 2 (N2).
Divide stitches by transferring one-half of them to Needle 2
Slide stitches from Needle 1 to the cable to allow for room as you begin the round. Position N2 so that you are ready to work across those stitches. This will be the beginning of the round.
Making sure the stitches are not twisted, begin working the stitches on N2. Remember that you are always working with the ends of the same circular needle. In other words, when working stitches on N2, use both ends of N2 - do not cross needles.
Continue across N2 working in pattern as instructed.
Turn work to continue in round across N1. Move sts from N1's cable to N1. Move sts from N2 onto cable allowing for room to work.
Knit across Needle 1 using the other end of N1.
Repeat these steps continuing around the work.
Need additional tips & tricks?
Check out Cat Bordhi's video on YouTube:
Or this video from KnittingHelp.com: