By not sending them to senseless wars in the first place?
aha! That's what immediately occurred to me as well, then I decided not to post it because sardonic rhetorical flair doesn't really answer the question.
I'd start by not charging their families for their funeral. See to it that surviving veterans get proper post-traumatic clinical service. The idea is for them to be productive members of the society, contributing to the GDP after their service. Job placement services might be useful. Anything that eases the transition back to civilian life is helpful. Most veterans do well with this, but for those who do not such services could make the difference between marginalization and productive citizenship.
