I will be starting my last year of FNP school next semester. I started in health care in 1990 as a Resp. Therapist. I graduated from BSN school in 2003. There is no way I would have been ready for FNP school without my Resp. Therapy background! As for post-graduation orientation for NP's, there ain't none. You'll be oriented to the charting method (paper or electronic), shown where the bathroom is, and that is about it. Basically you will feel like you've been (and you'll hear this a thousand times, by the way) "thrown to the sharks", because you will be thrown to the sharks. Hopefully your care providing colleagues will be willing and able to help you in the areas in which your are least self-confident.
That being said, Ive heard of new BSN grads going right into MSN-NP preparation. They must be really bright or in a very easy program. I'm not saying that it can't be done. I am saying that in my humble opinion it shouldn't be done, there is a vast amount of "stuff" that must become second nature to the Nurse prior to entering training for "Advanced Practice Nursing". Learn as much as you can in the Hospital, ask a bunch of questions, learn to read ECG's, X-rays, MRI's, CT's etc. well. Learn why the care providers order a certain therapy, versus ordering something else. Don't be afraid to be wrong!! You will learn a great deal be asking follow-up questions that require redirection by the provider giving the answer. It will mold your methods of critical thinking, problem solving, and logic.
Most of all, enjoy Nursing! Enjoy the fact that you are the only one around treating the patient, not the patient's disorder or disease process!!