House Rules

I've always sort of cringed when hearing people refer to the Player's Handbook or the Dungeon Master's Guide as a "Rule Book", even though that's technically what they are. However, I think anyone who believes that there are really "rules" in Dungeons and Dragons is sorely missing the whole point. I always go well out of my way to make sure I say "guidelines" instead of "rules".

D&D differs from other game formats, because as long as everyone involved agrees, the "rules" can be bent, broken, or completely revamped to suit the story. Over the last twenty years and more, my group of players has always played by a certain set of house rules that help make sure we stay on track as far as the goal of playing: fun.

• Max Hit Points.
  You're a fighter, tasked with spearheading a group of elite adventurers into the enemy's domain. Valiently you brave certain doom to protect your friends and emerge victorious. (ding!) You gain a level bringing your greatness to new heights!
  
  You grab your PHB, your pencil, and your character sheet. You've selected your next feat already, and all that's left to do is roll for your HP increase. /roll: 1. ...Talk about a suck-fest!
  
  You are the heroes here. You're supposed to be better than the average citizen. If the average citizen goes up in level, why should they have just as good a chance as you at gaining more HP? BS, says I. If you're at the table with us, you get max HP for your class. If your hit die is a d10, then you get 10 + your con modifier, period.
  
• Food.
  Within moments of being born, a baby knows it's hungry. Nobody goes off on a trip without making sure they have food, yet you, a seasoned veteran of adventure might forget? Pff...
  
  Food and water are things that we always just assume the adventurer picks up before they leave. Give your characters the benefit of the doubt here, even if the players behind them might be a but dull. Anyone conscious is going to think of food.
  
• Stats.
  If you're at my table, and I'm the GM, feel free to not bother rolling your stats. You want 18s? Go for it. That's right, you heard me, I don't care how you come up with your stat rolls. If all 18s is what it takes for you to enjoy your time at my table, go right ahead.
  
  This is of course based on the fact that when I generate a character, I've got the personality in mind long before I put pencil to paper, so if my character is stupid, I'm certainly not going to give him an 18 wisdom. I give my players that same benefit of the doubt. But like I said, you players are heroes! If you want to play a perfect scored fellow, my job is to make sure the game is enjoyable for someone controlling such a character.
  
  At the end of the day, the story will probably have little to do with the ability scores anyway.
  
• Leave room for style.
  If something doesn't really matter, leave it up to the players. For example, does it really matter what a magic missile looks like? It manifests from the caster, and stops on the target causing X damage. Who cares if it looks like a flaming tennis ball, or a blue streaming thing, or a beam of light? Let the player decide what it looks like. This adds a certain style to their character that helps the player define the character. 

Don't discard the books altogether, obviously. I'm not saying they're useless, there's an awful lot of material in there that is very sound, and should be observed, but if it gets in the way of your story... a little creative license isn't going to make a "TILT" alarm go off. Keep balance and fairness in mind, and loosen shackles!

What are some of your house rules?