When running a published adventure which some players have already played, such as a RPGA module, are there any suggestions for keeping it interesting for all involved ?
A lot of gamers enjoy familiarity with a classic module, yet want to play it again and again. Here are a couple of examples of ways you can do that so they will still have fun:
Play against expectations: If a player has already been through a module a few times, and knows that in the guard room in the first hallway there is a pit trap, move it across the hall or take it away entirely. Instead of a guardroom filled with goblins, have it empty, or the guards could be hiding a few rooms away. A few instances of this, the player will wonder what else you have changed, and completely lose confidence they know what is going to happen next. The levels of paranoia this creates are greatness!!!
Modify opponents: Say you are running the classic G1 Steading of the Hill Giant again and you have a few old guard at the table who know the module backwards and forwards. What are they going to think when suddenly the Steading has a couple of Hill Giant Shamans that can cast spells, or the guard wolves have turned into trained displacer beasts, or the Chief Nosnbra has a Ring of Invisibility? Again a few changes like this will keep both new and old players on their toes.
New areas: That player who has gone through B1 In Search of the Unknown half a dozen times is going to be mystified by the fact that dead-end corridor suddenly has a door...that leads to another cavern! Just adding a few secret rooms, some extra rooms, or a Temple to an Evil God where none was before will keep the returning player guessing
Even in an a written module there can be great variety in experience. Don't let the characters (NPCs) you've got to work with lie flat; breath life in to them. Draw on that acting class from college, make that villain despised.
The same thing with combats. Be inventive with the forces listed, and don't be afraid to make flavor changes.
Remember, the adventure is an guide, not a script.
Specifically for RPGA stuff: There's a lot you can do to alter the premise, the situation or the NPCs.
One example I've mashed up before is Many Hands Make Light Work (DRAG1-1). The adventure is originally about the PCs altruistically helping the Sisters of Selune rebuild a temple in the Dragon Coast. One common way I've reworked it is to have the adventure start in Cormyr (which is at odds with the DragonCoast) and have the PCs on a secret mission that on the surface is rebuilding the temple, but secretly, unbeknowns to the sisters of Selune, they have a mission to install a magical listening device in the temple and clear out the tunnels underneath for a safehouse. Selmik the rat can be it's own sideplot- it mentions him singing and playing an organ - a bit like Phantom of the Opera.. well you can turn that into a whole sideplot- he's an opera performer who's gone missing, affected by wererats. Although the module doesn't say so, the Temple of Selune specializes in curing lycanthropy. It's a great way to restructure things when you have all of these elements.
Similarly- for something like Scepter Tower of Spellguard, there are actually three adventures, but the real deal has to do with the Shadar-Kai villian collecting pillars in order to seize control of the oracle-ghost. Well, you can do quite a bit in the monastery and even outside of the designated adventure area by having someone approach the PCs and say "Someone stole an old white pillar from our museum in the Grey Vale recently.." and then implicate the halfling clan, Dark creepers, etc.. and then have the clues point the way back towards Spellgard. Normally- at least from what I've seen- Dms just run this adventure linearly- first the halfling wererat clan, then the tunnels, then the tower.. but you can really make this much more engaging by involving the rival adventurers at the monastery, and using the over-arching mystery of the magical columns. It doesn't have to be in order at all. The investigation can happen organically, and the NPCs at the monastery can be used to really make the adventure into an engaging mystery.
Continuity and mission is what you make of it.
In the past I have used the players' expectations and knowledge and used it against them by tweak various traps or changing the encounters. Or in a substained campaign world if the players have gone through it once then what would this adventure be like? What would have moved in since it was last explored? This is a fun exercise of taking a known thing and putting your own twist on it to make it new again.
Do a mash up. Grab a second module, perhaps with some kind of common element to the first, and mash them together. If the players are expecting an orc warboss in location 13b, and instead it's the ghost of a pirate captain, still searching for his lost treasure after all these years, then you've shaken things up without really changing anything.
If you're not comfortable with major edits to published modules, you can try other tricks to give the players a more immersive experience.
For example, In running one published module where the party ends up in a cave-in, we were playing in a relatively small, windowless room. When the cave-in happened, I read the box text then reached over and flipped off the lights, leaving the room in total darkness. "It is dark, you are likely to be eaten by a gru. What do you do?"
If a player lit a torch, I lit a candle.
If a character pulled a sunrod, I snap a glow-stick, shake it up and hand it to the player.
One player pulled out a cell phone to light his area. "What? I have dark-vision."
With all the players with a light source we completed the skill challenge and as the party emerged from the cave-in I flipped the lights back on.
Sure I had spend a few bucks on supplies, but overall I think everyone had fun.
Think of the module as a movie, or story where the stars are always different. What would happen if the star was a dark haired dark eyed cimmerian? How about a magic wielding swashbuckler? A famous detective? A dashing trickster?
Module NPCs are usually designed to hook the player characters into the adventure. Adding some complexity to the npcs beliefs and personality traits can make an encounter more interesting. ex: The missing villager may not want to be rescued by a paladin who worships his gods immortal enemy. In fact he may secretly plot to attack his rescuer as soon as given the opportunity.
Coming up with a few more personalities that are linked to the module npcs could definitely mix things a bit as well. ex: The wise old man could have a rival, the decrepit sage, who is intent on stealing the mcguffin and may offer the pcs a fine bribe if he believes they are persuadable. If not, he may hire someone else who will which may lead to ambush if the player characters are caught unawares.
I think this is a huge gift to you as a GM - if they are already familiar with the bones of the adventure, that frees you up a lot! Ask them to fill in details, paint scenes, offer descriptions, since they know where they are and what is about to happen. If you are all on board, I could see this being a very fun and collaborative session! You can spend more time on details, senses, and motivations. When it comes time for encounters, change things up enough to keep it exciting and unexpected.
Old Adventures have old NPC's.
One thing I Love about a old Adventure module is all the NPCs that might remember the characters. Nothing brings them back quite like "Its them guys, The ones who cleared out the hill trolls. Your not going to beleave this but those trolls are at it agin".
You can creatively modify the quest for the passage of time.
The quest is essentially the same maps and the same NPCs. But the ones that were killed off might need to be replaced, maybe there's new monsters in the area as well. The basic quest plot elements are unchanged but there reason for doing things may have changed. "Dreadbeard's brother is holed up with a bunch more trolls looking to settle an old score, thats why I sent that letter for you he's been causing trouble. We'll gladly match what we payed you before".
Adding any important elements you can remember from the last time the is simply a must.
Old gamers get a great kick out of seeing things there characters did brought up in game. Its a great way to tip the hat to players who completed the adventure last time. reminding them of the fun they had last time and drawing them back into the story. Not to mention new players to the adventure can here first hand the heroic tales of the first time they players hit the dungeon up during the breaks between game play. "That's why there's only three towers because the trolls took refuge in the fourth one and the fighting brought it down".
This may only be relevant to dungeons, but simply moving the connections - whether they are clues or dungeon corridors - can have a big impact. The whole area of a dungeon can be different if you switch a few connections around. Players will no longer know the exact direction to go. If you also change some traps and move the encounters based on the new map shape, it will keep players off-balance.
Alternatively, simply consider what the adventure would be like if the PCs arrived before or after they are meant to. Perhaps the orcs dug a second tunnel for an emergency exit? Maybe the ogre lair moved to higher in the mountains? The murderer the PCs are chasing may have already killed the person who asked for their help, or maybe hasn't even started killing yet. This will confuse players as well, but can be done to make either small changes or larger ones, depending on your preference.
A method that can require slightly more work is changing which NPC employs the PCs. If it's the local authorities, the PCs can get away with more than if it's simply a concerned citizen. Also, if the job is changed slightly from 'stopping the attacks' to finding the attacker' the PCs priorities change: they may risk more lives being lost so they can catch the killer instead of simply stopping him. Of course, for many adventures the easiest way to do this is to only pay the PCs if they bring the BBEG back alive.
You may also (to completely change the adventure without needing to change any locations/people) simply change which side hires the PCs (and maybe add some antagonists from another adventure). If the small kobold tribe wants protection from treasure hunters instead of the PCs attacking the dungeon, they defend it from the vicious goblins. This can interest players who have already played the adventure, as they will see the opposite side of the story.
The specifics will depend on how balanced you want the modified adventure to be, but in general, these techniques have helped me before in many ways.