The cause is usually not enough light, or the light is very directional (for example if the pot is near a window). The remedy is to turn the pot regularly (i.e. every day or two) to keep the plant growing straight. You can't "straighten out" a plant that has grown as twisted as your picture, though. Best to start again from cuttings, as in the other answer.
If you really want to "start from scratch" with this type of succulent, gently pull a few of the lower "leaves" from the stalk and put them somewhere clean, dry, and well-lit (but not scorched with strong direct sunlight). The don't need any compost, and in fact they are less likely to rot or get other diseases without any compost. There is enough water stored in the old "leaf" to start off the new plant. Pot them up when they look like the picture, which may take a week or two.
(Image source: http://gardeninggonewild.com/?p=24797)