Re: When to start applying.....
start applying now. you can inform your employers of when your preferred start date and when you actually graduate/take the licensing exam. if you wait until you're ready to start working, you may find many jobs already taken by nursing students from other schools (or from your own).
when i was a student nurse, we graduated in august. the nurse managers who came to our class to recruit told us to wait until may to apply for jobs. when we started applying in may, guess what? they told us they'd already filled those positions, but maybe in a couple of months they'd have something open up. so, you either have to 1) wait a couple of months on the off-chance that a unit you want to work on might have a spot for you to try for, and mooching off your spouse/parents in the meantime, or 2) work somewhere you don't necessarily want to work because you absolutely have to have a job.
trust me, there are no negatives to jumping the gun and applying early.