When I learned to knit, I was only taught one bind-off, the standard knit two, then pass the first stitch over, then knit one, pass one to the end. That creates a pretty tight bind-off edge, which is often less giving than your cast-on edge. Sometimes, you just want a stretchier edge, for a sock that won't pinch or a sweater that will fit over your head. When you'd like a looser bind-off edge on your knitting, there are two main techniques experienced knitters will recommend.
The first loose bind-off to learn involves knitting (or purling) two together. You knit two stitches together, which gives you one stitch on the right-hand needle.
Slip that stitch back onto the left needle.
Then knit it together with the next stitch.
Repeat this all the way across, until you have only one stitch remaining on your needle (when you'll cut your yarn and pull the end through that last stitch, as usual). By eliminating that pass-over stitch, you are eliminating the move that constricts the stitches on a bind-off.
The finished bind-off edge.
To make this bind-off stretchier on the knit side, knit through the back loop. To make it stretchier when purling, wrap your yarn counterclockwise instead of clockwise.
Another popular loose bind-off method involves yarn-overs. Adding in that extra amount of yarn is what keeps the bind-off from being too tight. For this method, start your bind-off row with a yarn-over on the left needle. Then knit the first stitch and pass that yarn-over stitch over. Now you are ready to start the repeat. Yarn-over, k1, pass the yarn-over stitch over, then pass the first stitch on the right-hand needle over. It's like the standard bind-off, but with a yarn-over thrown in.
The look of your needle as you're ready to pass off the first stitch. The yarn-over is the middle stitch.
Always remember to pass the yarn-over off first.
For this bind-off, you'll need even more yarn than a usual bind-off row, so be careful if you're playing yarn chicken at the end of a project. (You know, where you think you have enough yarn to get in just one more row, so you don't bind-off yet and then sweat out the entire bind-off, worrying you won't have enough yarn left.)
I quite like the look of this finished bind-off edge.
One variation on this bind-off is to make the yarn-over a purl-wise yarn-over. So the yarn goes in front of the needle underneath, then comes up and over.
For either method, always remember to truly achieve a loose bind-off, it's important not to pull your yarn too taut after each stitch. After all, the whole idea is to avoid making your bind-off too tight.
So the next time you're knitting a bottom-up sweater for a growing kid, think about using a loose bind-off method. The stretchy bind-off might even last through a growth spurt.
What are your favorite loose bind-offs?