Within the last two weeks there have been a couple Emergency threads with decent info in them.
With no real first hand knowledge on their testing, I assume it'll be your basic writen and skills. All the companies test about the same. They know you guys are new and a lot of the real learning comes from being out in the field. They just want to make sure you're not a complete dunce. I've yet to hear of an LA/OC skills exam to be "Let's pretend in this next scenario that you're a paramedic, now run this megacode!"
The interview is really where you're going to make or break it.
I started applying to companies almost a year after taking National Registry. I spent a couple weeks before starting applications retyping all my notes from EMT school. You don't need to be that extreme, but spend some time reading through your notes and watch the skills DVD. Also, not that it'll be on the test, but go to OCEMS' site and read through the different policies and familiarize yourself with where the different Trauma, Stroke, STEMI, and Burn hospitals are.
Based on one of the threads, I know Emergency is actively hiring. Doctors, PacifcRM, and Lifeline are also looking for people. Get in where you can in this business, get some experience, then move on to somewhere that provides you with the environment you want to work.