To use newly spun singles for knitting or crochet, all you need to do is wash the skein and hang it to dry. Since it's singles, it may twist on itself a bit; I don't like to put too much weight on my singles if I'm going to knit or crochet them, as the yarn will re-twist on itself when you wash the knit/crochet item -- so usually I hang a handtowel through the lower loops of the skein while it's drying, and that's enough to keep the yarn tame without stretching the flex out of it while it's drying.Singles can be great fun to knit with -- if they are super-energized, you can use that to your advantage to knit zig-zag scarfs (do 20 rows stockinette, 20 rows reverse stockinette, repeat until yarn ends); or you can knit garter stitch to "even out" the biasing of the yarn. Most of my singles are fairly low twist, and they merely have one "post" of the knit stitch vertical and the other at an angle, without any noticeable bias in the knit fabric at all.
I haven't experimented with singles in crochet, but a friend who spins-and-crochets crochets with her singles all the time and I've not noticed a bias in her fabric.
For details on washing skeins I can recommend this blog entry of mine.
And I've a few postings on spinning singles yarn, feel free to browse the list that comes up in del.icio.us.
The singles in the picture are from a Totally Tubular Spinning Kit, the knitting is the start of the newest Ewe'niquely Yours pattern, Touche: Arm and Wrist Warming Sleeve.
