If you can afford it, I would suggest Addi Turbo's. They are awesome. I find the circ's much easier on my wrists, shoulders and neck. I relax my arms more, and the cord takes the weight of the knitting, not my arms.
Cast on like you normally would. The stitches will still be on your left and your newly formed stitches will end up in your right hand just like straight needles.
Turn the needles around so that all your stitches are in your left hand again and your right side is empty. You will still have a right/wrong side.
This probably sounds so confusing. Once your brain adjusts, it will all make sense.