What is the #1 most important thing to remember about DMing?

[racoffin]

To tell a good and engaging story.

 

[Stormonu]

The #2 item on the list is that it's the player's story, not yours.

Of course, the #1 is to have fun; everything else is just guidelines and opinions.

 

[NewJeffCT]

be organized. I'm not good at making stuff up on the spot, so I've found being organized helps me better deal with those times the PCs do something unexpected (which usually happens hourly in my games)

 

[NewJeffCT]

make sure every one gets a some spotlight.

very important - and, knowing which players generally need more spotlight than others.

 

[Rel]

Cardio.

 

[Theo R Cwithin]

Be impartial: don't play favorites (and especially not toward NPCs/DMPCs)

Wear pants. And by pants I mean trousers.

 

[Raven Crowking]

If you stop having fun, stop.

 

[ThirdWizard]

Watch the players' reactions and adjust accordingly.

A good DM can create a fun encounter. A great DM can create a bad encounter and still make it fun.

 

[Diamond Cross]

Be fair, but don't take argumentative and manipulative crap from players. When your decision is final, it's final.

 

[billd91]

You're not there to maximize any one person at the table's fun, you're there for the fun of the group as a whole.