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.