1. You need to ask questions. (It is not good to “know it all” during the interview even if you know the key things to you.)
So, perhaps, “What software does the firm use for calendaring?” or “What would a typical day for a calendar clerk be?” or a golden oldie-but-goodie, “Is there an advancement path at the firm if I start as a calendar clerk?”
2. In this case, you are working translatable skills rather than direct experience. You need to relate for the interviewer what experience in your current job would apply directly to this job. (I am not sure exactly what that is, obviously, so view these as merely suggestions of types of things to say.)
What do you bring to this firm, tinyfaerie? “Well, in my current position I have similar experience, because I am juggling multiple clients’ schedules. I use Software X and Software Y for my planning and scheduling.”
“I am a real quick study with new technology, and I am sure that I can pick up your software quickly. When we converted from SoftCal to AccuSked, I was named one of the “Go To” team to answer questions for my co-workers.”
“Because I have dealt with the court system on a regular basis in my job, I know the ins and outs of scheduling there well.”
To generalize what I am trying to convey, avoid things like “organized”, “quick learner”. Instead, paint a specific picture that demonstrates those qualities and relates your experience to what the new job requires. Being forced to tell the story will also slow you down and stop the “rattling off” phenomenon.
3. As to the why you haven’t made it through to hire yet, it is a tough job market for one.
Other possibilities: In the case of a law firm, in particular, are you toning down your personal expression enough ( long sleeves over the tats; remove less-accepted piercings) for a pretty formal industry?
One thing you could try: Did you hit it off well with any of the people you second interviewed with? if so, I would call them, remind them who you are.
Don’t under any circumstances ask why you did not get their job.
Instead, say, “I really enjoyed meeting you and respected your style of interviewing. Can you give me tips as I go forward in my search that would help me in a second interview situation? I have another one this week, and would value your input.”
Finally, looking for a job can bring you down. You are a bright, talented person (apparent from your answers here). You will succeed. Hang in there.