Being an OMS-1 at SOM currently, I thought I'd leave a few nuggets of wisdom based on the experience I had during the application round last year:
1) Send your secondary in early (SOM doesn't screen for secondaries) but don't fret if you don't get an invite immediately. Plenty of my classmates didn't interview until March or April of this year. I interviewed in October, and I seem to have had one of the earlier interviews among those accepted. (In fact, one guy I met got accepted on the day of the white coat ceremony!)
2) Don't feel apprehensive about applying if you're an OOS applicant. My state of residence was/is Ohio, and I was accepted no problem (statswise, I had a 3.6/31). Some people on this board have expressed apprehension about SOM's reported 99% in-state student composition, but that 99% figure is in fact a bit of an illusion. Why? Well, up until this year OOS applicants could immediately become NJ residents when they became UMDNJ students, and the in-state tuition savings is substantial. Because of this, almost everyone took the option to change their state of residency, and it usually looked like SOM drafted incoming classes made up almost exclusively of in-state students. However, this year the rules regarding residency changes have been modified and now OOS students can't change their state of residency until their second year. Judging from the people in the class of 2013 that I've met so far, I'd say the in-state/OOS ratio is more like 80/20, but I don't have any official figures to back this up.
3) If your interview doesn't seem to go well, don't lose hope. Quite a few classmates I've spoken to have said that they didn't feel their interviews went particularly well.
4) Expect this application season to be competitive. UMDNJ-SOM received a record 3,500+ applications last year, and one of the staffers in the admissions office told me that as of one week before orientation the application volume was up 200% over last year. The overall acceptance rate last year was under 5%, and it only looks like it's going to get still lower this year. On the other hand, it seems as though the school is aiming to increase the size of its incoming class by at least 15 students next year - which will give the class of 2014 an overall size of about 150. (From what I've heard, the class of 2013 was originally only supposed to be ~120, but they ultimately decided to accept 135.) With any luck, the increasing number of seats in the incoming class may help balance out the additional competitiveness caused by the skyrocketing application volumes.
Feel free to PM me if you have any other questions.