First, never lie. Second, present facts in the manner best suited to support your claims.
There are a lot of facts you can start gathering now, to later hand to a Veteans Service Officer from one of the veteran's groups. In particular, all your medical records.
There seems to be a need for strategy in dealing with the VA. Most VSOs will tell you that your initial application will be denied, but the VA will provide their reasons for doing so, giving the VSO a strategy to meet the VA objections. I feel that offering as strong as possible an initial application is important because there is a good chance you will be awarded at least partial service connection on some issues, but perhaps not on others.
When I prepared my own VA claim years ago I was assisted by the Paralyzed Veteans of America. Their help was excellent, but it was my own idea to get a letter from the PVA's medical director (a retired Navy Medical Corps rear admiral) to support my claim. Hard for the VA to object to that doctor's expert opinion! I also had the idea of getting separate medical opinions on chronic pain, chronic fatigue and other conditions. I had the idea of having my wife, who has a graduate degree in Human Relations Development, to write her own letter detailing as an expert and intimate observer my medical condition and impact on my activities.
All of the VSOs are extremely busy guys, trying hard to meet the needs of Iraqi/Enduring Freedom vets as well as all the rest of us from previous wars. They can use all the help possible from a client they represent. I suggest bringing to them as complete a package of your case as you can formulate. Include a one page summary addressed to the VA stating your claim, the general proofs offered and records attached, and you can do much to get these documents together now, well before you sit down with a VSO.
I recommend filing NOW an FOIA with the Department of Veterans Affairs addressed to your regional office if you have been treated by them before. Search through those documents for supporting materials...I was able to find a note made by a ward nurse that I'd had numb hands and feet following a 1992 surgery at Bethesda, and that buttressed my claim for peripheral neuropathy. I recommend filing now an FOIA for your military medical records, because in there you'll have all your flight physicals, notes of DNIF's, etc...and again, you can pull out supporting documents for submission to the VA.
I was able to find in mine the records of hip surgery I had for acute perhiperal neuropathy done in 1975, a year after I started flying in C-123s, and thus was able to establish service connection within the one-year time period the VA allows for that problem...and I had no idea where else to turn for old records as the private doctor had retired and the hospital records only go back 20 years. To file an FOIA with the Air Force, simply go to their web site and complete the on-line process...easy and fast.
To be accepted, an FOIA must state precisely what you need, why you need it (in our case, "for medical records to support my VA claim"), that you request the FOIA be expedited (in our case, "because I am currently ill and seek medical background to help guide my treatment"), and that you are willing to pay a certain amount but request that the fees be waived. You need to provide your address, telephone and email. It helps to suggest that you would accept email or recorded media (CD, DVD) in response.
A veteran's claim is also supported by letters from other veterans who have knowledge of your situation. These are called "buddy letters" (either in letter form or on the special VA form they provide, VA21-4138) and the VA must evaluate them. Case in point...John Harris established his service connection to Agent Orange with a letter from a buddy who saw him on the ground in Vietnam during a battle damage check. John Harris and other aircraft commanders have prepared generic forms which state that the aircraft flown were assigned to the 731st TAS, that Air Force records indicate they were used as spray aircraft in a UC-123K or C-123B configuration. John's letter, plus copies of your flight orders or other documents placing you on duty aboard the contaminated aircraft, complete the proof we have to offer the VA. You must also have Agent Orange-presumtive illnesses, and that will vary with each of us. This is where we can help each other, and why we need some sort of organization to our group of C-123K veterans.
One tactic I've been working on recently is soliciting letters of support from scientists and physicians by asking them to review the various Air Force tests done on the aircraft, and offer a conclusion as to our service on the aircraft leading to exposure to the toxins indicated on the Air Force studies. Oregon Health Sciences University did such a conclusion for us, and it is posted on the links section for your download. Please try to get such support from universities or other experts you can reach out to!
Doctor's letters are important, although the VA considers its doctor's opinions as more accurate than other opinions, yet they will yield to the weight of your evidence when you provide multiple letters, multiple conclusions in your favor. Such conclusions must state that your condition "is as likely to as not" be caused by exposure to Agent Orange toxins (dioxin). The VA discounts such passive "may" and "possible" as less than 50%, but statements of "as likely to as not" or stronger conclusions such as "most likely", "highly probable" etc. are weighed as greater than 50% in the veteran's favor.
After I had heart surgery I started my search for causes of various illnesses and chanced upon the Air Force tests done on C-123K for Agent Orange contamination. At my next meeting with my cardiac surgeon, I gave him as strongly worded a letter as I could formulate, asked him to read it and consider providing me one in his own words with his own conclusions, and explained the importance of his letter in my VA application. He gave me almost exactly what I needed. I believe every physician seeing you for an Agent-Orange related illness should be asked for just such a letter, to go with your VA application.
Finally, if you've submitted your claim in the past and have success strategies to offer, please send them if for us to share.