One thing that was particularly valuable was ensuring every proposal came with a "alternatives" section (called "competitors" in the NABC model). We also made sure that every proposal included "do nothing" as one of the alternatives, to provide an anchor for a discussion about what would happen if we simply didn't take on the problem at all (or stuck with whatever imperfect solution we were currently using).
I often scroll to the alternatives section first thing to see whether at least a few alternatives were honestly evaluated. Too often I just find some bullet points with abstract URLs (without any summary for the reader) and a statement that they would not be as great as the proposed solution - or no section at all.
It becomes impossible to provide constructive feedback at that point. It leaves me with the dreaded “Have you considered Alternative X, Y, Z?” or a passive-aggressive “Could you do an unbiased research of alternatives against the requirements?”
Even though the alternatives section tends to be towards the end of the document it doesn’t mean that it should be filled out at the end.