What tips do you have to navigate VES or Veteran Evaluation Services?

I am assuming this focused on preparing for a VA disability initial submission, follow-up or appeal to the Department of Veterans Affairs.
1. I highly recommend contacting DAV, VFW, or any other veterans service organization [VSO]. They have offices dedicated to assisting service members by translating the language of [US Code] Title 10 service-connected injuries and illnesses into [US Code] Title 32 VA disability submissions.
2. Ensure you have a copy [hopefully more than one] of all your service medical records and any civilian medical records during your period of active military service. I highly recommend making pdf copies of all records and storing it on a thumb drive.
3. Start the process no later than six months before your retirement/ETS. Your personnel office should be able to help you by providing information and perhaps contact info for VSO folks who are available to help you navigate the process and follow-up.
Thank you my friend SSG Carlos Madden for alerting me.

Get and keep copies of everything you send or upload to the VA. I can’t tell you how many times I have faxed papers with confirmed receipt and they still don’t know where it went. Never send small bundles of papers. Make sure that each is numbered with a breakdown of the numbering on the second or third page. This will give them quick access to notes on specific things being provided or contested. Summarize all your doctors appointments and test results for everything claimed. Get letters from doctors if they will not file a DBQ or ask for all documents from the office of the doctor. There are notes that will be there that you are unaware of. And get this book. It’s not cheap but it is the resource of champions!

Get access to all your medical records, get advice from others that have been through the process, and don’t wait until after you have officially separated to start the claim process if possible.

Find yourself a good Veteran Service Officer. Here in Oregon each county has a Veteran Service Office (at least the counties I know). Also, make sure that you have all your medical records prior to exiting the service. I have worked with many veterans that didn't and are now trying to get the information. Buddy statements may also be key in getting your claim approved. If something happened and there is no record in your files, and we know that we didn't go to sick call for things we should have, a letter from a witness can help a lot. Be persistent. The VA will possibly deny your claim. If you feel that they have denied something that they shouldn't have, appeal. A lot of this does go back to having an advocate that will work for you. Any VSO worth a damn will. Just make sure the VSO that you go to for assistance has your best interest in mind. If a VSO is asking for money, look somewhere else. In most cases it is illegal for them to ask you for payment. But some can take a percentage of the award though. A lawyer can ask for payment though and in some cases, a lawyer is definitely warranted. Don't be afraid to ask for help. We know veterans "like" to do stuff on their own, but there are so many nuances, changes, and rules to know, there is no way the average person can keep track. Let the experts work for you! I have had good experiences working with most Veteran Service Officers that I have interacted with. But there are some that call themselves such and are far from it. And also just some that really suck at their jobs. So be selective.

Never give up. They will disapprove you over and over trying to get you frustrated and hope you will quit.
It took me 30 years to get a favorable response and I think it was because I keep at it all though I did quit for about 16 years.
I did notice one thing, After Bush was elected the first time I was approved in a year after I submitted my request.

This is NOT a Medical issue when it comes to fighting for your earned benefits, it is a LEGAL issue. Once you realize that this is about crossing "T"'s and dotting "i"'s the issue becomes a lot easier. I recommend reading the entire CFR regarding your rights, but for disability Ratings, This is what you NEED to PROVE legally using medical documentation and Buddy Statements...
"https://www.benefits.va.gov/warms/bookc.asp"

The Good News is that you can Hire a Lawyer to help with the process but it will cost you and I would recommend waiting until the Appeals process before resorting to spending your money. Also Everything that you submit has a TIME PERIOD that needs to be adhered to, Don't Miss and try not to reschedule appointments, they are hard to get.

The difference between a 90% approval and a 100% approval is your ability to show patterns of behavior or rituals that stop you from functioning on a daily basis. If you say "I have PTSD because of -----" then you will get 70%. But if you say "I have PTSD because of ‐----- and everytime -------happens, then it triggers me to ---------- every time." And then you show a pattern of how many times you reacted doing that behavior. You have to be numb to your own pattern of behavior instead of going in there telling them what's wrong with you. Hope this makes sense.

I didn’t know anything about them when they first contacted me. They tried to give me the impression they were part of the VA. I was slow to realize they weren’t advocates but actually hostile investigators looking to nullify my claim. I don’t trust them to do what’s right and now avoid them whenever possible.

Get an attorney. If you are approved for VA disability, they will do every single thing possible to reverse the decision. They will literally lie, cheat and steal to reverse it. (I have proof) GET A 20% LAWYER.

Get off the grid if you can