So you want to learn how to knit a wizard hat. Some knowledge of knitting is required - the knit stitch, and knitting in the round, and k2tog decreases. Soon I will add measurements so you can adjust this pattern to fit the size of your head, but until then you will just have to make wizard hats which fit me.
Cast on twenty stitches (or any even number, if you want a different size. If you want to make a wizard hat twice as big as mine, you can do math to double every number of stitches I mention. That's totally okay) on eight of the double-ended knitting needles, in the round. You should have a string of 160 stitches by the end. Knit one row, so you have a single row of 160 stitches in the round.
On the next round, do a k2tog decrease on the second stitch of each needle. There should be a k2tog decrease every 19 stitches.
Keep doing this, with a decrease on the second stitch of each needle, until there's only 10 stitches on each needle.
Do one round and discard every other needle as you go around. What I mean is that when you reach the end of the first needle with 10 stitches, instead of using it to knit the next 10 stitches, keep going with your original working needle until you have 20 stitches on four needles. Make sure you don't discard the noticeably different needle - it'll come in handy later. This isn't necessary but it makes it easier.
Keep going with 80 stitches for as many rows as you like. Seriously. Go nuts. Just make sure you still have a significant amount of yarn left. This is the tube part that'll fit on your head.
This is where the fun begins. Keep knitting around and around, but every time you reach the noticeably different needle, do a k2tog decrease on the second stitch. If you've got a different way of making sure there's a decrease every 5/4ths of the way around, you're allowed to use that, but I found that was a very good way of keeping a nice even cone shape. If you'd rather a more noticeable staircase shape, you can do four evenly spaced k2tog decreases every five rows. That's okay too. This is just a smoother way of doing that same amount of decreasing.
When you get to the end (1 stitch left on each of your needles), you can end however you like. I like to keep going with k2tog stitches until I have 1 stitch left and then I tie off, but you can do anything you like. I also tend to tie a pom-pom to the top, but that'll be a different tutorial.