This is my first attempt at making a hat. Not enitrely happy with the may it sits, its made from some old cord i had lying around, but i'm quite pleased with it

excuse the surly look

my arm modelling it (a bit lighter, this one)

this is the lining for the head band

Right. Tutorial.
This is, i've made two different hats now, i've only got photos for the one that is slightly different, but i'll show you how to make both.
Oh, you'll need
Card/thin sheet of cork (i used this for the later two)
Some sturdy fabric, if you are using thick demin, prepare to break all your "jeans" needles.
A little fabric for the lining
optional- button for top of alt hat.
For Both, you need to start with a "visor"-like base.
measure your head, and then add about 4cm to the measurement. This isn't all seam allowance, as you want your head to be able to "breathe" and you don't want to be walking round with a permanent headache. My hat size is 56, which is a S/M , so i use 60cm of fabric. Cut this measurement about 8cms deep and do the same with the lining fabric.

cut out a "peak" out of a piece of card/cork, and if you like you can double layer it. Draw round this on your fabric (wrong side, obv) and sew two pieces together to make a pocket for it. When you've made that, turn it inside out and put the peak in, and sew it up as tightly as you can. You might want to use a zipper foot for this.

Lie the peak in the middle of the right side of the head band fabric (bit you cut out earlier) and sew it on, staying as close to the line you made earlier.

Sew the ends together and try it on your head. It should be a quite loose, but it shouldn't fall straight down onto your shoulders. Sew the lining also, and sew the hem bit down.

(heck, this is long..) Right sides together, sew the lining to the head band. BEFORE you sew it, check that when you turn it round, Right sides out, the peak is in between.

now you can make the rest. or have a rest...
Original (train driver) hat
Halve the measurement of your head (56/2=28) and add 6 (34). cut two pieces out 34 x 8 cm. Obviously if you head is a lot bigger add more. This makes the floppy bit above the head band. Sew ends together so you have a big loop.
Pin this to the head band, making little even pleats. Its worth getting this right, so give it a few goes.
You now need a circle with circumference 68 (or whatever your new measurement is, *2). You can wing it, or use your computer calculator, c=2pi x r, so 68 = 2pi x r, so 34=pi x r, so r=10.8, you need to make a circle with radius 10.8 cm.
All you have to do now is sew that to the rest.. woohooo you should have a hat. (make sure to tidy up the lining by triming the other edges, folding over them and sewing the lining down)
OR my (preferred) jockey hat

fold a piece of A4 paper in four, and then fold that quarter in a triangle, and you should end up with something like this: (after a bit of cutting)

You need 8 of these, i recommend drawing straight onto the fabric, it helps get a better line later. Sew them all together like a parachute, and then fold down the edges and sew them down. (this makes a big difference, so don't cut corners).
Very careful (and painstaking) pinning onto the headband should give the right look, then sew. Again, tidy it up by trimming the main fabric seam edges, and folding the lining over and sewing.