I think all the relevant points have been covered above, but still here is my €0.02 worth...
Take head of cabbage and prepare. Remove undesirable leaves. Quarter. Cut out cores. (Keep cores, as desired, they're fine to go in as desired.)
Weigh quarters (and pieces, if included). Remember weight. (Better, write it down.)
Thinly slice quarters. Can be done by hand, or a mandolin makes easier work of it. If using a mandolin, watch the finger tips. Or use a food processor with slicer.
Place shredded cabbage into v. large non-reactive vessel. Add salt at 2% weight. e.g., metric (easier): 1 kg = 20 g; US (/Imperial): 2 lb = 0.65 oz.
Mix, cover and leave it sit for a bit. I go and do something different for 15-60 minutes.
Get in there with both hands and simply clench both hands into fists around the kraut to squeeze. Release and grab a new load. Repeat until a good amount of liquid is released, or one is bored.
Optional: leave sit, covered, for a bit more.
Now just jam it into a suitable jar. Press down to release further liquid. Pour in remaining liquid from vessel. Once all is in there decide whether to add further brine, also at 2%. Aim is to cover completely, by 2 cm / 1 inch. Add weights if necessary.
Seal (with airlock, or whatever) and wait desired fermentation time. Typically about a week.