The main thing I try hard to adhere to as a DM is trying to say "no" as little as possible and not letting the rules get in the way of a memorable scene. In a game as highly collaborative and creative as Pathfinder - or any tabletop RPG, really - is all about imagination, from both sides of the table. So, when a player says, "I wanna slide down the bannister on my shield, jump off at the end, and then swing from the chandelier all while hacking at the people below me," you can see where a strict application of the rules could really hamper that. So, when a player goes out of their way to be super creative, I think a good DM steps out of the way and helps them accomplish that goal.
Now, I've been a player in a group when the DM very much stuck to the rules, most of the time to the detriment of the group. I had a neat idea for a Paladin who had an irrational fear of water - due to the fact his sister drowned and his family blamed him for it - and he was haunted (literally) by her water-logged shade. He flat-out said no to the idea, because Paladins are immune to fear... I ask you: would it be game-breaking for a Paladin to have some kind of uncharacteristic flaw? I say no. This is why the above is so important to me. I felt really creatively stifled in that game, and there was no real good reason for it to have happened that way.
I'm not meaning to toot my own horn here. I actually learned this from the DM I try so hard to emulate. Thanks, Corey!
