I think part of the reason we get so many 'how do I do an lj cut' requests is because the phrase "LiveJournal specific tags" doesn't necessarily mean anything to the user. They don't know what tags are, and there's nothing about that word that leads them to believe this 'cutting away my entry thing' would be called a tag.
So I'd like to suggest a change to perhaps:
"How do I use an lj-cut? What are the other LiveJournal specific tags?"
The 'What do they do?' of the original title is, in a sense, fairly redundant--I'm in a FAQ, so of course it's going to tell me what something does, because that's the point of a FAQ. So if that text is removed, it makes room to specifically spell out the most commonly-asked-about tag, the lj-cut tag.
Anyway. Just a suggestion, of course. Thanks!