I follow Sandor Katz's method (Wild Fermentation). I use a stoneware crock, and for every 5 pounds of cabbage I toss in 3 tablespoons of kosher salt. Mix it up, pound it down and break the fibers with a blunt object (I use a pestle), and repeat the process.
I use a dinner plate on top of the cabbage, held down with a plastic 1 gallon jug of water on top of the plate, to keep the cabbage under the brine. A linen cloth over the top to keep the bugs and other debris out. I usually use 10 - 20 pounds of cabbage per batch. I skim off the top stuff about every other day once the fermentation kicks in
. I'll probably keep it in the crock for 2 - 3 weeks and use a taste test for what I want. This method hasn't failed me yet.
If you need extra brine, 1 teaspoon of kosher salt per cup of water.
IHTH