I hope that Navy HPSPers will find this helpful since I know it can sometimes be frustrating trying to do everything correctly. Here are my observations and what I learned going through the Navy match. I got what I wanted.
Overall, I think that if you want to do HPSP you need to be ok with doing a GMO since you are signing on for the needs of the Navy, which are always changing. That is the decision I made before signing on the dotted line. I was ok if GMO that is where I ended up. However, with that said, if you want to have your best opportunity to get what you want (be it deferral etc.) in the Navy GME-1 match, here is the advice I have after having gone through it.
1.
Make sure you do Navy rotations. Do NOT think that by not going to a Navy facility you will sneak under the radar and get a deferment because they don't know you. I have heard of one person who tried this and it didn't work the way she had hoped. Set your rotations up early where you want to go. Figure out what specialties you want to do and call or email the med student coordinator many months in advance. I did like 8 months in advance. The new coordinators are great and really on the ball. If you don't hear back after a while follow up. This whole process is about you being organized and being proactive. But it will work if you are on the ball. If there are others from your school in Navy HPSP coordinate with them to make sure you all are getting the same information and finding out what you need about clerkships, housing, and paperwork needing to be faxed for the rotation etc.
2.
Make sure to INTERVIEW for NAVY GME spots. When you are rotating on away rotations say at San Diego, Bethesda, Portsmouth, be sure to set up interviews. Again, the clerkship coordinators are really great (I interacted with San Diego and Portsmouth). They will help you talk with whomever you need to, so if you have a question make sure to see them when you show up so they can take care of it and get you in touch with the right people early on in your rotation.
3.
If you are thinking about a deferral...then you really need to be on the ball with knowing the process. This is a lesser known process and if you aren't asking the right people in your specialty about then it isn't going to happen. Initially find out who the specialty leader is for the Navy for your deferral specialty. Contact this person. Don't be scared to get in touch to find out what is going to happen that year. i.e. How many spots there will be for deferment that year, Who you need to meet to interview with, when the deadline for paperwork is etc. If you are serious about deferment then make sure you know where the specialty leader is so you can interview if you need to and at least do a rotation in that specialty somewhere with the Navy.
This year it looks like there were 8 Ortho, 4 Neurosurgery, 5 Anesthesia and 8 Emergency Medicine deferments. The numbers of deferments aren't definite until the the selection board meets each year, as this year there were only supposed to be 4 EM deferments, and it could have been fewer, but then they gave out 8 when they finally met at the selection board. So you never know.
If you are going for a deferment then rank it number one and fill in your reason in the optional personal statement on the Navy rank form. You will have also interviewed for some Navy spots so that way you can list a few things as well for your backup plan.
4.
Ranking your choicesfor the Navy match. This can be hard to do depending on what you want. Just know that if you list it then the Navy thinks you will be happy getting it, so even if it is number 6 on your list, if you couldn't stand ending up with it then don't list it. The only downside is that if you aren't competitive enough and don't list enough things to get one then you could end up with a 1-year deferment or a phone call from the selection board asking you to do something else. I don't know how often if this actually happens, but that is a possibility.
5.
Read Everything provided to you. There really isn't any excuse not to read all information provided detailing the process for what is a very important step in your life. Make sure you are familiar with what is going to occur with the process.
http://nshs.med.navy.mil/gme/NAVMEDGME.htm
This way you will know the process and important dates and be able to ask educated questions. Read all Navy emails sent out, make sure they have your correct Email address on file and you have been receiving emails from the Navy registrar.
Anyway, these are just all my thoughts. Hope you can take what is here without attacking my comments and use them to help you get what you want in the future. The needs of the Navy are dynamic and so there is no way to know how many spots in a specialty will be needed until the time comes. The process can work and get you what you want, I think I read 85% got one of their top 2 choices this year in the Navy Match on a post here somewhere, but I do know it can be really frustrating and cause a lot of stress as you wait for the match to come to a conclusion. Best of luck.
The Navy HPSP Office in Bethesda was pretty good about sending out all the email information you need for the process and there is plenty of time. Don't be nervous unless you procrastinate and don't pay attention to directions.