Gathering information before heading off to face the dangers of dungeon or wilderness is always a smart idea for players in old school games. Probably the most iconic example of this is the classic rumor table, as appearing in a handful of old modules from the Holmes-Moldvay era of D&D. My first experience with the concept, as it probably was for a vast number of old school players too, was the rumor table in B2: The Keep on the Borderlands. The idea is valuable and sound, but I can think of some ways it might be better implemented.
First off, some rumors ought to be assigned to specific NPCs, or to certain types of NPCs, e.g. guards, merchants, beggars, and so on. Some rumors can be widespread and available from any fool on the street, but others are more appropriately disseminated by select persons. Not only does this often make narrative sense (the woodsman should know more about the owlbear that's made the local forest its territory, and the merchants' guild officials naturally have the inside dirt on the recent bandit attacks on commercial traffic) it also gives players a reason to seek out and talk to these NPCs rather than idly questioning patrons at the tavern until they're sure you've rolled every possibility on the rumor table at least once.
Secondly,
every rumor should reveal a truth about the campaign. Even the "false" ones. I can't stress this one enough. Instead of throwing out random and arbitrary false rumors to mess with the players, think a little bit about why someone might believe a misleading rumor to be true, or alternatively why he might spread it if he doesn't believe it, or even knows it to be false.
1. The rumor is based on someone's actual observation, but is mistaken as to its meaning. A hermit who lives in the woods often sings loudly and horribly off-key, leading to a rumor that the woods are haunted by tortured souls.
2. The rumor is based on someone's observations, and the witnesses have been deliberately misled. A clan of goblins wear boots with ogre-foot-sized soles to leave ogre-sized tracks to scare away interlopers, so naturally the rumor spreads that a terrible ogre will kill and eat anyone who trespasses in his domain.
3. The rumor has a kernel of truth but is wildly exaggerated. The sensational has a certain cachet and staying power that the merely factual often lacks. People love to embellish stories, sometimes without even intending to distort the truth. That quiet fellow in robes who frequents the library and apothecary but says not a word about what he's doing? Obviously a powerful wizard who'll turn you into a toad if you look at him cockeyed. The juvenile dragon that moved into the cave on the bluff with a pile of copper pieces? A world-destroying monster that sleeps atop the hoards of seven kings!
4. The rumor is true, but the NPC relating it doesn't believe it. Sometimes the truth is just too wild to be believed. The rumor, when it is repeated, is told with heaping dollops of sarcasm, scoffing, and eye-rolling. Those who do believe it will probably be mocked, and the person who started it may be a laughingstock in the community.
5. Confirmation bias. The facts of the case are more or less agreed upon, but minor details and interpretations are twisted to reinforce the teller's pre-existing opinions. A local outlaw claims to be the lost heir to the throne. He's definitely working to undermine the current king, but is he an impostor trying to usurp power, or the rightful ruler here to depose the tyrant? Depends on whom you ask.
6. The rumor is started by someone seeking attention. While other attention-seekers may pass it on as second-hand news, the players won't find many other witnesses who can corroborate it directly. It's probably best used as obvious comic relief rather than a serious lead. Naturally, these are almost always complete rubbish, but once in a while, such a rumor could turn out to be mostly correct, to the surprise of everyone, including the rumormonger.
7. The rumor is started by someone who stands to gain from it. Said person might actively perpetuate the hoax by staging or planting evidence to be found by others. An herbalist might put out a rumor of vampires to sell garlic, a king may sow rumors of invasion to scare the populace and justify draconian rule, or a crooked merchant might tell of a treasure in a nearby cave, where hired thugs await to relieve treasure-seekers of their equipment and lives.
It should be noted that many of these possibilities reveal more about the people who spread the rumor than its actual subject, and those kind of things have their most interesting and useful effects in a campaign in which those people are recurring characters. It's more fun when players can develop a sense of which NPCs can be relied upon, which ones are deceitful, or gullible, or concerned about their image more than the truth.
