A simple declaration: It should somehow be made IMPOSSIBLE for a President to engage the country in an elective war (e.g., Iraq I or II, Bosnia/Kosovo, Haiti, etc., but not necessarily war with Japan after Pearl Harbor, nor with Afghanistan after 9/11) without simultaneously doing two things:
1) Instituting a fair draft to ensure that the threat to life and limb is widely shared and that the people are appropriately involved and engaged (that'll get their attention).
2) Establishing a special, direct funding source exclusively for the war, to ensure that it is paid for (to avoid robbing ourselves of other priorities without our avowed consent).
As it is now, wars are too freely waged with our standing armed forces. Then, once the war is underway, if it becomes necessary to extract more soldiers and money than expected at first, the people's other priorities are set aside, willy-nilly, with precious little citizen representation at the table. Whatever flag waving and parades are necessary can be arranged. All this under the rubric of national emergency: "We're at war, pal - cough up!".
Actually, my real reason for this proposal is to get the people's attention. A good whack on the head (or across the face) is what's needed sometimes (heck, probably all the time). Only by requiring definite actions by the government to provide adequate sourcing for personnel and funds, at least coincident with but preferably before, waging war, will we be sure we have the people's attention. Besides, it's just the responsible way to manage.
Will Rogers used to joke that we shouldn't be able to have a war until we've paid for the last one. I've always liked that sentiment, so let's credit old Will for the genesis of my proposal. Only this is meant as NO JOKE -- I'm deadly serious, as is this topic.