Jeez Ross, a little bitter are we?
For the player: If a player really wants to do something, they will argue with the DM for an uncomfortably long time especially if the argument in question doesn't change the story or the outcome of the game in any way, shape or form.
DM Laws (because I believe in being fair and balanced):
If the DM emphasizes one particular solution more than any other, then he is going to fuck you over.
If the players come up with a better solution than the ones the DM has provided, then the DM will fuck you over.
If the players get really interested in the game and are anxious to play that week, then the DM will play a one-shot of a game that no one has ever heard of because the game is so "underground" that it is impossible to find in stores and can only be bought off of a special website or at a convention. That means the game has streetcred.
As the DM, it is your job to throw a ton of subplots at the wall and see what sticks. If players suddenly remember a subplot or character that they enjoyed from a previous game, then get all pissed off at them for caring about the world you have created.
As DM, you should keep a very detailed NPC list of all the characters the players have encountered as well as any characters you might have mentioned in passing. Update the players on the status of all the NPCs from the great hero that the entire town loves down to the lowly town crier that had one line in session 5 and has never been seen again. If you don't keep this list, the players will and you do not want to suffer the consequences.
Dms should never pay very close attention to which monsters are considered a player's mark, their quarry, or any other stupid title that the players give monsters as they battle them. It will just give the DM an unnecessary headache.
Remember DMs, players can't just go fight a dragon, they have to go through the following steps: get the dragonslayer sword from the wise old man, but he won't give it up unless you give him a special gem that grows in the magic forest. You can't enter the forest without a blessing from the water spirit, but you have to please her by finding her lost daughter. Her daughter has been captured by a cattle baron and the only way to beat him is if you star a riot on the ranch. Even if you start theriot though, she is locked in the bathroom and the key has been stolen by a band of tieflings. And guess where they are? The magic forest that you can't enter without a blessing from the water spirit. In short, make sure the players are fucked from the start.
The most important law: If players love something, then kill it.
I love you Ross and to show my love for you, I got you this gift.