First, what is an lj-cut? An lj-cut is a feature lj has that will essentially hide whatever's under it until someone chooses to click on it to view.
Nobody's going to mind only a couple words, sentences, even paragraphs... But several pages worth of writing can be annoying. Especially as we get several updates here a day.
Now... How does one make an lj-cut?
That's it! :D