Buford... I'm DEFINITELY no expert on this... but... I use a small metal file that fits nicely into my backpack pocket along with my other emergency arrow making/fletching gear.
I put the arrow shaft onto something sturdy (like my leg or a log) with the broadhead extending out over the edge and tilt it slightly.
Holding it firm, I then get the file and give it a couple really hard goes... on one side of the broadhead. I then flip it, and give a single, firm, but not as hard as the first, going on the same blade edge. I try to make both filings at about 30-45 degrees.
I then feel it... and so long as it's really sharp... I then give one final file - very gently just to take the burrs off.
This seems to work for me. They're not as sharp as Adam the Punisher's broadheads (which I think he uses to shave his head these days?!), but they work for me.
I learnt this from watching others, and experimenting a little