One of the first skills that every new knitter should learn is how to insert a lifeline into their work. Lifelines are great because if you make a mistake in your knitting you can rip everything out back to the lifeline then slip your stitches back onto your knitting needles.
Lifelines are also helpful when you are working an afterthought sock heel. Placing lifelines on either side of the waste yarn that marks the heel makes it easy to pick up the heel stitches later.
How to Insert a Lifeline
Practice inserting lifelines and knitting afterthought heels with the "Feeling Loopy Socks" pattern, available in my pattern shop.
Thanks to Skacel for providing the yarn and knitting needles I used to create this pattern. These products are available locally at many yarn shops and online at Makers' Mercantile.