I just finished my first sock but the top is too tight to go over my heel. I used the long-tail cast-on, should I have used a different one?
The long-tail cast-on is a sturdy one, excellent for when you need structure, but not so much when you need stretchy. Better choices, in turns of stretch, include:
- cabled cast-on (super easy)
- tubular cast-on (to go with 1-1 ribbing)
- rolled edge (easy, durable, and would let you still use the long-tail method)
The links are for TECHknitting, but these are well known techniques and a web search will bring up lots of resources for any of them.
If right-handed knitting, lay your right pointer finger tip on the needle while casting on each stitch to make sure there's a space between the stitches. Then spin the needle clockwise all the way around before casting on each stitch. I got this from the "Learn the Elastic Cast-On with Knitting Expert Patty Lyons!" video on the https://www.youtube.com/watch?v=nA3CFC2MYDY page.
Then, if you need a stretchy bind-off that's done in a similar way, try Lori's Twisty Bind Off:
Sometimes the issue is not the cast-on but the number of stitches and the way that the sock and leg are shaped.
I have knitted several top-down (and toe-up) socks based on my foot circumference, which is how most patterns are measured, and been unable to fit them over the heel as written. What helps there is to plan for a few more stitches at the cuff and adjust the decreases after turning the heel.
If you knit a swatch or gauge sample in the round before you start the sock, it'll be easy to see how many more stitches are needed at the cuff: measure your leg's circumference at the height you'd like the sock to be.
Another potential constraint is the height and depth of the sock heel itself. Lengthening the heel flap may help, or if you're knitting a sock with a short-row heel, consider adding short rows (which can be tricky for the heel's overall shape). Two heels with more depth, or easily adjustable depth, relative to a standard short-row heel are fish lips kiss and sweet tomato.