There are a few methods to use when knitting the crown of a hat. Most hats are worked in the round on circular needles. However, as you get close to the top of the hat, working the decreases, the hat becomes too tight to continue using circular needles.
There are a few options you can use. This option is Magic loop. This method uses a long circular needle to work the decreases on the crown. You will need a long circular needle, the same size as the circular needle you are using to knit the hat.
This video shows you how to magic loop to work the decreases.
I have created 2 other videos with 2 different options to use when working the crown decrease:
You can choose which method works the best for you.