As I understand it everything the DM ever conveys in relation to the game, and I mean everything, is a clue. What I should have said in my prior post is that the DM can give hints, but hints are referee's actively being generous to the players.
What you can do, if folks are getting frustrated, is make some judgement calls a little more in their favor. I've found this can work as a clarifying question from me. For example, if a player is openly talking as if their dog isn't with them, but it actually is, then I'll read a phrase a little more helpfully like, "Where did I leave my dog?" is followed up by me with "Are you looking for you dog?" If yes, "Blitzberger sees the dog walking along beside him" or some such. (The tricky part is this may blow a player's cover who may be attempting to bluff another player, so watch out if a hardcore group falls into your lap)
It's kind of a catchphrase for me now, but my most common question is, "What are you doing?" Asking me stuff like, "Did we turn off the stove before we left?" isn't really anything I can answer. For me, D&D's largely a memory game played in the here and now.
And, y'know what else works? When the players have an idea that's wrong, but doesn't contradict anything that's happened in the campaign, it suddenly becomes true. Why? Because that's a lot more fun.
I used to do this in the past, but I actually enjoy being wrong as often as not now. (Not that going with the group's current preference isn't another satisfying style or anything) What I've found is sticking to a single (yet dynamic) situation can help with focus and get people concentrating on what's happening as well as what did and what might happen. Of course it can mean the PCs going off in all sorts of directions where what they expected is not at all what occurs, so this isn't for everyone.