I'm a new DM running my first adventure in D&D 4e. I've heard of the "three clue rule", that there should be at least three independent pointers to any plot element you want the PCs to take note of, in places where it's likely the PCs will find them. This seems to be mostly working. The players are good about recognizing a clue as a clue when they find it. However, the problem is that the players have extremely short memories, and often forget they're carrying around a crucial piece of evidence, even when I have NPCs ask the PCs what proof they have of their assertions.
I'm at a loss for what to do here. Should I punish them ("Your words are worthless, maybe a stay in the dungeons will teach you not to make false accusations"), ignore their lapse ("I'll believe you...this time"), or what?
Similarly, they completely forget about minor quests ("return the stolen cask of ale") that they've gotten from NPCs questgivers, even when other NPCs remind them about it. I was counting on them completing the quest in order to give the PCs a reward (namely, better weapons). Should I withhold the reward or just give it to them anyway?