There are many ways to increase stitches in knitting; these are some of the most common.
Yarn Overs for Different Situations
While the most common yarn over -- between knit stitches -- is pretty easy to figure out, yarn overs needed in other situations can sometimes cause confusion. Here's a look at all the different kinds of yarn overs you might face.
Knit in the Front and Back
Knitting in the front and back of a stitch (kfb) is a relatively easy way to make an increase. If the name isn't explanatory enough, here's a look at how to do it step by step.
Purl in the Front and Back (pfb)
Purling in the front and back of a stitch is an easy way to increase, but it doesn't feel particularly natural or intuitive when you do it. Here's how the stitch is made.
Make one or M1 is a common increase that's mostly invisible. It can be a little tricky the first couple of times, as it is a little tight, but once you get the hang of it you'll be using make one everywhere you don't want your increases to be obvious.
The lifted increase can lean to the left or right, but is somewhat less visible than other increases.