There must be at least 2 dozen cast-ons out there. I only know of maybe 5-10 but that's been enough for me: long tail, stretchy long tail, I cord, backwards loop, cable, provisional, estonian, mobius, etc. Many of them are shown on this blog.
My standing favorite is long tail because I like the edge it produces for most garments.
This video iknitwithcatfur by does a great job of slowly showing the process.
Since this method uses the intended ball of yarn, one has to guess at the best length for the tail part, often resulting in a quick frogging of the cast-on stitches even before starting the project due to running out of tail. That can be so frustrating. Some folks overcompensate by leaving a really long end to cut off before beginning and it can feel wasteful.
A few weeks ago, I needed to cast on 350+ stitches. I am pretty good at estimating to about 200 stitches on long tail but really didn't want to have to start again after I got to 305 or 340 or even 345. Actually that's the reason I don't do or design many bottom up shawls. Most of them start with over 300 stitches and that amount of casting on can seem not only endless but rather discouraging if it all has to be started again and again.
So there I was trying to decide on a length for the tail when I noticed I had 2 balls of the needed yarn.
It was an epiphany for me. I know some of you already know this, but self discovery is so cool.
I took one end from each, knotted them together, put one ball on the floor, one ball on the table, used the knot for the center and knew I had way more yarn than needed but could cast on happily until done, then cut off the second ball to use later.
Then I got to thinking about how to use only one ball and realized one could take one strand from the center and one from the outside and do exactly the same thing. Of course this will only work with a center pull ball, but mostly that's what I use. I love figuring stuff out and sharing it with you.
For those of you participating in our La Mer Mystery KAL, you will need to put your skeins into center pull balls. Decide which is the MC and which is the CC. I suggest if you have Woody and Panda to use the Panda as the MC. If you have Panda and Donegal, then use the Donegal as the MC.
You will also want to learn a stretchy long tail cast-on for this project. This is the German Twisted. There are others too but whichever one you use, make sure it is stretchy. Practice this. When you are comfortable, cast-on 351 stitches and have patience until Sunday when you will receive Clue #1.