"A great frustration is when someone, usually a fiddler, starts up a set of tunes and by just imparting a little info could have guitarists providing at least a basic accompaniment."

What information would you want imparted? I've tried saying "this is a set of reels in D" and watched (mostly pop and country trained) guitarists just sit there like dumplings with no idea what to do. Am I supposed to come with a chord chart written out in felt marker
and hold it up? Something short of that must work, surely?

All I want to know is what key it's in, and whether it's a jig, reel, hornpipe, slip jig, slow air, or whatever, and I can usually accompany it (it would have to be something pretty weird for me not to be able to). If it's more than one tune played as a set, I'd like to know in advance which key each tune is in, and how many times through, or ideally get a nod or shout from the leader just before the change, and again before the end. Doesn't always happen that way, but I can usually cope!