Backwards Loop Cast On

Cast On Techniques
Also known as the "single cast on" this is the simpliest cast on of all. It can be used for casting on stitches in the middle of a row (as for a buttonhole) but it is all too often quite sloppy and loose. If you need to cast on in the middle or at the end of a row, it's often better to do so by knitting on (seelast issue). I'm including it now because the tubular cast on that I'll be talking about next uses it as its base.
To work this cast on, simply make a backwards loop and place it on the needle.

Repeat until you have as many stitches as you require.

Tubular cast on
The tubular cast on is, to put it mildly, a gorgeous way to cast on for working ribbing and has been praised for its loveliness all over the knitting blogosphere. Using a spare piece of yarn cast on half the number of stitches you need using the backwards loop cast on. (If you don't know what that is then you're not reading the entire article. Go back one technique.) Then, using the working yarn, purl one row. Now take a minute to look at what we've just done. Notice that there are purl bumps of the blue working yarn peeking out from between the loops of the wine colored waste yarn. We'll be using those bumps in a couple of minutes, so remember what they look like.

Then work 3 more rows in stockingette stitch (knit one row, purl one row, knit one row) and turn the work so the purl side is facing you for the following bit.
Purl the first stitch. Next insert the right needle into the first purl bump way back down on that first row you purled -- the ones were were just inspecting.

Slip the loop onto the left hand needle and knit it through the back loop.

Continue across the row, purling 1 stitch, then picking up and knitting tbl the next purl bump until you come to the last stitch. Purl the last stitch, the pick up the loop at the selvedge edge and knit through the back loop.
Turn and work ribbing, knitting the knit stitches and purling the purl stitches. Remove the waste yarn by cutting between some of the stitches and tugging to remove lengths of yarn.