There are advantages to knitting socks toe-up. For example, the sock can be tried on as you go, so the fit is perfect. If you are not sure you have enough yarn, you can knit both socks at the same time and stop when your yarn runs out. There are various ways to start a toe-up sock: Figure-8 cast-on, provisional cast-on, long-tail cast-on combined with grafting, etc. I used to use the figure-8 cast