Sorry to bump an old topic but theres a few points from the many campaigns I've ran.
You as the DM are a storyteller, but it is NOT your job to magically save characters when a mistake is made or a trap is set. Many problems with PC's is the fact they put their own personality into their character instead of playing the character inside the box so to speak. Setting DC's for not your average feats of strength / dex is common. They always had the chance of going "We're not prepared for this, lets go back and regear" Too many players are hack and slash anymore and don't realize.. "Hey we can run!". It always depends on the group you run.
If you have any questions or want tips and tricks on dungeon crawling / generic rules of thumb let me know deadly. A book will only get you so far running a campaign playing helps and making mistakes as a PC will make you a better DM. I've incorporated a few things that a lot of my PC's got messed with in the game because it was something that is easy to rig, common to see, and takes a bit of thinking to get passed. It all depends on how you want to play it. The slayer, the thinker , the talker or maybe a bit of all three.
