How to make a hood

Get a bit of fabric which is at least 4 feet by 2 feet. Fold it in half (with the 'good' side on the inside) so you get a piece about 2 feet square. This is the basic shape for a hood - draw it on the material, with the top of the pattern against the fold of the fabric. Make it as big as you can to start off with, you can always make it smaller later and your head is bigger than you think it is! Don't unfold the fabric, just sew a line down the edges marked in green, about 1cm in from the edge. Sewing up the front (the green line at the left of the diagram) is not necessary, you can use a button or toggle instead as shown. Once you have sewn the back of the hood together (the curved edge at the right) you will be able to wear the hood (but keep it inside out). Check that the head and face holes are big enough.

Damn! The face hole is too small!

Unpick some of the stitches at the front. This might cause the whole hood to sit higher on your shoulders but at least you can see out!

Argh! The head hole is too small!

Well, cut it bigger next time... but all is not lost, instead of sewing up the front, use a toggle, with a long bit of string to loop over it to make an attractive 'sits back on the shoulders' hood instead!

Once you're happy with the size, hem all the edges marked in red.

Variations

Instead of a straight bottom edge, try a 'battlements' pattern - this looks very Robin Hood. It's a faff to hem, but worth it. Or try a zigzag. For a really silly 'pixie' hood, lengthen the head point (top right of pattern). You can make this as long as you like. If you're being really silly, put bells on it. No, please don't.

This pattern is pretty basic, you might need to refine it as you go along.