When I started my first pair of socks (a couple weeks ago), I followed the exact instructions in "The Twisted Sisters Sock Workbook." The toe-up method involved a provisional cast-on.
When I started the second sock, I decided that there was no point in doing a provisional cast on when I'd figured out (in that blank mental state when knitting stockinette in the round) a way to cast on normally, and make a nice-looking start for the sock.
I know I'm not being very clear (pictures to come soon), but it goes like this: Using DPNs, CO 16 st (exactly what you'd do for provisional CO). Knit the first st. Take a third DPN and knit the second st, making sure to not wrap the yarn around needle #2. Alternate knitting a st on N2 and N3 until you've knit all the st (8 on each needle). Then K the st evenly onto the needles (4 st on each).
I occasionally think, "Why not just CO 16, and k 4 st onto each needle?" Then I remember that that would mean sewing the toe together at the end, and this cast-on is trying to avoid as much finishing as possible. It creates a fabric that is automatically upright; that's not a very good analogy, and I'm really not a good enough knitter to be able to come up with an explanation for the shape of the fabric, but it really does work.
And now, of course, I'm going to get a half-dozen emails telling me the name of this cast-on that some highly renowned knitter invented/discovered/laid claim to. (I immediately thought this when I "discovered" the technique- someone's probably come up with it already.) Anyway, I'm proud of myself, and I don't care if I've re-invented the Alternating Stitch Cast-On.