I've been having great success lately with my "Just Start Knitting" toe-up sock method. Here's how it works:
I take a circular needle, 40 inches or longer for working Magic Loop, in the size indicated on the yarn band. (I knit pretty tightly, so others might want to go down a needle size. Use your intuition). Then I use Turkish cast-on:
- Hold your circular needle so that both ends are together, pointed to the right.
- Pull the bottom needle to the right, so your top needle is held together with the bottom cord.
- Start your yarn in back of the needles, leaving a 12" tail hanging.
- Wrap the yarn down toward you, down across the front and up the back of the needles.
- Knit half a round, across the stitches on one needle.
- Hold working yarn and tail together, and work 1 round. This doubles the number of loops on each side.
- Drop the tail, and knit one round, working a stitch in each loop.
Then I begin increasing for the toe. And by the time I'm approaching the desired circumference for the size I intend to make (usually about 8.5 inches), I have enough worked that I can check the gauge and whether I like the resulting fabric. Not much time invested, so it's easy to start over, but if it's good, then you didn't waste that time doing a gauge swatch.
One note, though: I typically overshoot the increases by one set. I can't tell until I've worked an inch or two, and often I have to frog back (or in the case of the "Deathly Hallows" socks, improvise by adding ribbing and some cable twists). Then I keep knitting, and wait for inspiration about how to do the heel.