I would like to hear your experience on what not to do, in a Darksun campaign?
What was your biggest regret?
“Mixing up Gold pieces, with Ceramics, in a treasure” Was my all-time biggest bummer.
It made the pc. rich enough to by out house Shom.
Everyone is entitled to their opinion on how things run in their specific setting, so keep it civilised.
Hmm, a couple thoughts:
As a DM, I’ve learned to never have NPCs important to the plot be less than 2 levels higher than the PCs(otherwise the telepath will charm him, the rogue will slit his throat, and the halfling will eat the corpse).
As a player, never leave the city without enough water to last you twice as long as the estimated travel time(unless you’re a water cleric)
In an ancient ruin, NEVER tell PCs there is a metal door…
Never let any cleric other than Water or Rain have any spell that creates water 
From a player’s point of view.
Don’t expect an Elf to be honest.
If you hear a strange sound in the wildress, don’t investigate, just run away. It’s safer.
Letting mid level or higher PC’s participate in the Red Moon Hunt is always a bad idea…no matter which side of the hunt they are on.
1.Don’t tell the halfling pc that everyone could be considered rations. 2.Don’t forget to remind the halflin pc that his party members don’t count as rations if you screw up and forget #1.
Defaulting into “regular” fantasy tropes, like dungeon crawl, save the princess, or encroaching monsters into the village.
Staying away from this makes it harder to be creative, but you can also re-skin stories:
Instead of a dungeon crawl, the players fall into an ancient halfling ruin or an empty settlement
Instead of save the princess, you have to find a powerful psion and bring them back
Instead of encroaching monsters on the village, slaves keep escaping and attacking guards
Replace"halfling" with “thri-kreen” and “everyone” with “elves” for an additional good rule
Depends on how often you’ve been swindled buy the pointy eared thieves.
Can’t resist replying as so many responses actually made me laugh and nod here.
As a PC: 1-Deciding that our party was strong enough and had enough experience to journey from Urik to Nibenay in a straight route overland, and not along the “roads”… and that it would be better to do the moving around at night to save on water and “it can’t be any worse than traveling during the day.”
2- Ever letting myself think in the format of “it can’t be any worse____ than ____” As in, “The tall grass can’t be any worse than the barren wastes…”
3- Letting myself think the “dungeon” or “quest” would be the hard part of a game rather than surviving the elven market, the journey to the destination, and the journey back laden with whatever stuff we managed to get… and then trying to sell it all off in an elven market again…
As a DM: Not vociferously stressing maybe the 10 man party, 6 of whom were new to Dark Sun, should look at skills like survival, craft, appraise, at least 1 “social” skill, and orisons like Create Water or some of the early Psionic powers I was letting people choose from that might be able to let them mend their gear… As in yelling at them with a megaphone “You will die without this… faster than you otherwise would!” But the one that takes the cake is in the same 10 man party having the 2 kreen players convince me that since they’re insectoid they should probably benefit from a perpetual Spider Climb effect despite the rules saying they can not climb walls in such a fashion, explicitly… and then watching them coach other players into loading up on haste and various spells that let them hide, move silently, or otherwise blend in to their surroundings. I was a Sigourney Weaver short of re-creating a sci-fi movie with that one.
As a PC: 1-Don’t forget to buy a cart if you’re digging through ruins (Okay this applies to all DnD settings, but come on guys, why does everyone keep forgetting to do this? You don’t start the game with bags of holding…)
2-Don’t apply the morality of other settings to Dark Sun. Fastest PC death I ever saw, first session our ranger tried to beat up the templar and free slaves in the middle of the bloody city. This was after we explained the setting to him in depth. I chalked it up to a learning experience. If you’re going to do that you at least need a plan.
3-If you buy hirelings, remember that they need to eat and drink like the rest of us. Long story short this lead to a 3 week trip in the wastes and our heroes subsequently abandoning their hirelings in the middle of nowhere once supplies were dwindling. The halfling didn’t appreciate this waste of emergency rations, but the group talked her down.
4-Don’t try to ride an erdlu. This is a personal favorite of mine because of the weird way the ADnD books were written, so erdlu were priced and described as if they were mounts. In reality their size, strength, and behavior is more akin to sheep. Needless to say hilarity ensued when our gladiator showed up on one and I promptly made my own writeup detailing the mounts from various sourcebooks to avoid future confusion.
DM Advice 1-Don’t let your PCs ride an erdlu (unless they’re halflings I guess). Okay yeah so for the first session I actually didn’t understand how these animals worked either and we only figured things out after a few re-reads.
2-Learn how psionics work before starting the campaign. Okay so full disclosure, I did learn the fundamentals of psionics when i started, but basically all of us were playing psionics by ear while we played. Not the best time for anyone.