I rather like sauerkraut and enjoy making it from time to time. The other day, someone wanted to know how to do it. Here's what I told them :-)
Chop cabbage quite finely (I use the grater function on my food processor, but otherwise cut it as fine as you can by hand). Measure it by packing it down tightly into some kind of measuring cup/bowl, then put it into a bowl that fits it with lots of room to spare. Add one dessert spoon salt per 2 cups (packed) of cabbage and toss to mix it well.
Pack it tightly into wide-mouthed jars. I use 1L glass jars (like mason jars) and one big cabbage fills 3-4 of them. Put something into the mouth of each jar that's fairly rigid and goes right across the surface of the cabbage. I use lids from honey pots - the kind of lid that's a bit flexible and kind of peels off the container that it comes on. Here in NZ you get that kind of lid on containers of honey, yoghurt and icecream. You want something a bit flexible so you can poke it through the mouth of the jar (which is a bit smaller than the inside width of the jar) but then goes right across the width of the jar inside. If you don't have anything the right size you could hopefully find something that's too big and cut it down.
Leave it somewhere warm. In NZ, most houses have a 'hot water cupboard' - a cupboard with a big boiler that heats the hot water for the house in the bottom of the cupboard and then shelving above it which is usually used for drying linen etc.. I use this cupboard for most of my fermentation as it's a bit warmer than regular room temperature and the heat is very stable there.
After a day, you'll find that the cabbage has lost about one third of its volume. At this point I usually move it some of the cabbage from one jar into another so the jars are full again and I don't need to take up so much space in the cupboard with my jars. Make sure you put the plastic lid and weight back on again.
Leave it in the cupboard for a few days until it's how you like it. I generally find 5 days is about right for me. Then take off the lids/weights and put proper lids on the jars. Keep the sauerkraut in the fridge from this point on - if you leave it at room temperature it'll just keep on getting softer and more sour. It keeps practically forever in the fridge.
If you find it's a bit too salty for you, before you eat it put it in a seive and run it under the cold tap to rinse off the excess fluid.