This Rule is a little trickier to implement. I interpret it as not accepting last minute interviews. If someone calls me up about a job, and they want me to interview that very same day, I tell them that I'm busy, whether I am or not. You can't let recruiters and employers treat you as if you have no life other than them. On the contrary, your life is very full and busy, and you're doing them a favor if you can fit them in!
Besides, when they have to wait to interview you, they're wondering whether or not you have other offers you're considering, and if you're interviewing elsewhere. It's none of their business; should they ask you, you tell them that you have been asked to keep such things confidential. That's not a lie; Shocking Pink is formally requesting that you keep such things under your hat! It's a very good indicator of how you stand for the position.
If they're calling you well in advance, the position is a planned opening, the company is stable and has things together. If they're calling you at the last minute, things sound harried or rushed, or the position's open because someone left and they need to fill it in a hurry - you know the company's a pain to work for, and they'll treat you badly if not with indifference. Observing this Rule strictly will of course cut down on the number of interviews you go on. That's fine; you're already not wasting time on companies that would only have caused you heartburn. And The Rules are all about avoiding needless pain and not wasting time.
Suppose you have lunch planned with a friend, and a recruiter wants you to interview at that time? You tell them you already have a commitment - but of course you don't say what it is. You already know to schedule your interviews very early in the morning or very late in the afternoon. You're in demand. Or you appear that way. Let them ask you when you're free next. Make it convenient for you. If every recruiter in town is rushing to throw their candidate in, never mind; your chances wouldn't be that good anyway. Who wants to waste time wading through a maelstrom? If you have a choice of days on which to interview and they're willing to accommodate your needs for a particular time slot, they'll show you a lot of consideration both as you interview and on the job. If a recruiter calls you up and says that they're going to submit you for a job and the interview is already tomorrow at 2 PM, in what kind of regard are you held? You're just a commodity. Besides, you should always try to be the last one they interview for a position. It leaves the strongest impression in their minds.
Spontaneity is a bad word. That should happen during an interview, such as when you both discover you were in the same sorority in college. It shouldn't be a recruiter that's able to call you up right after lunch for a 3 PM phone screen. (Or worse yet, a "go-see" at his office.) The Rules say to treat dating like a job. Well, you should treat all activity around getting a job just like Rules-based dating! They're both serious business. You're identifying something you want, and working hard to get it. Stay focused on the end goal - don't make the mistake of winning the battle only to lose the war.