These are some of the best, general house rules that I've encountered in my time as a player.
Rule #1: Everyone Gets Max Hit Points. Everyone.
There is nothing more frustrating than playing a barbarian or a fighter and through the power of ill-luck winding up with fewer hit points than the evoker with consumption. While being turned into a glass cannon can lead to creative uses of resources and unique methods of compensation, that doesn't make it feel any better when your hard-hitting melee combatant concept has become a one-hit wonder in the wrong sort of way.
That's why one of the best house rules I've ever come across is that everyone gets max hit points according to their level. Everyone, at all times. Don't even bother rolling.
|There is a catch, though...|
This rule is a bit of a double-edged sword, though, because it means the monsters get the same deal. On the one hand, this means your party is going to be in for a challenge when they come into the dragon's cave, but on the other hand it also means that you won't end up with a weak final boss because the bugbear chieftan rolled minimum pips on all of his hit dice when the DM was putting the sheet together. You simply calculate your max, dust your hands off, and get back to adventuring!
Rule #2: Re-Roll 1's (And Sometimes 2's) During Character Gen
This might seem like a pity rule to some players, but those players have obviously never seen someone like me roll stats for a new character. Adventurers are supposed to be different from the common populace, and every now and again these characters should have a lower-than-average stat or two that makes their strengths seem all the more heroic.
But what do you do when you have a sheet that's a single 10, and all the rest are single digits?
|Hell, even my charisma is an 11.|
If you roll 4 dice and drop the lowest number you've got a half-way decent shot at creating a workable adventurer. If you allow players to re-roll 1's then you've made the minimum stat you can have a 6 (something I think we're all comfortable saying is a big enough hurdle to overcome). Again though, this is a rule that cuts both ways, since your DM should use the same creation rules for NPCs and villains.
Rule #3: Deathblow Narration
This one doesn't have any mechanical benefits, but it can get players more involved during combat. It's particularly useful for groups where combat is already a big slew of numbers, and you want to try to slowly inject RP into things. Dealing a deathblow to a monster is always reason for a little excitement, and getting players to ride that wave by describing how the rogue's dagger slid between the orc's ribs, or how the ranger sank her final shaft into the wizard's throat before he could cast another spell, is pretty easy to do.
Not only that but it makes player narration something special. If you're not part of a RP-heavy group that narrates every attack and defense in combat then handing the mic to the player when he or she drops a bad guy is a great way to put emphasis on what just happened.
|If you have Cleaving Finish you only get a single narration.|
Rule #4: Death Monologue
This is another way to keep RP going, and it often lets characters go out like the badasses they should be when, inevitably, someone dies.
The idea of the death monologue is that the party are the heroes on the big screen, and if they're going to go out they should get to say something as they cross over. Perhaps the paladin, upon finally being brought low, says something like, "No, that's all right, there's no need to carry me," implying that her soul is already being escorted to the after-world. The barbarian, upon being impaled on the blade of a black knight might spit blood in his helmeted face and growl, "Be seeing you real soon," before finally dying.
|It also makes zombies creepy as hell when they mutter the same thing over and over.|
Death monologues are ways for players to inject one last moment of awesome into a character before decisions have to be made by the party. For instance, the rogue might have been a brash, cocky, know-it-all, but when he died clutching the cleric's sleeve and begging for forgiveness with blood flecking his lips, that kind of visceral going-out might motivate the party to at least try to bring him back. There are questions, whose answers they might not know any other way, and the player will get the chance to see how being dead for a little while affects the character.
Do they fight harder to prove they're still worthy of heaven, or do they try to balance out their mis-deeds because even a few hours in hell is enough to light a fire under them?
Rule #5: Cure Spells Have A Minimum... If You Want It
We've all been in that situation; the chips are down, the party is bleeding, and it's likely that at least one party member is going to go down before the fight gets finished. The cleric chants, holds her holy symbol aloft, and presses her hand to the fighter's wound healing him... of less damage than the monster's strength modifier.
|Saw that one coming.|
There are certain things in Pathfinder you just shouldn't leave up to chance, and one of those is using a 4th level spell and hoping against hope that you don't roll a whole bunch of 1's. In order to take the chance out of this roll it may be a good idea to let healing spells (or harm spells used to give HP back to undead) automatically heal 5 points per d8 that would be rolled. You can still roll, if you think you can get more, but that guaranteed minimum is often a lot more helpful than the fickle finger of fate.
And as with all of the previous rules, this one applies to the villains as well as to the heroes.
What Makes A Good House Rule?
Most of the time house rules are meant to solve specific problems in specific groups. One DM may feel that halberds are reach weapons, so he gives them that property. Another may feel that reach weapons should be able to be used against adjacent enemies as a swift action. Some DMs will change initiative rules so there's only one roll per side, and others will make it so disabling traps is a multi-step process instead of a simple roll of the die.
House rules are often judged on a case-by-case basis, but the important thing to remember is that house rules need to be applied unilaterally, and regularly in order to work. And generally speaking house rules should take chance out of something, rather than put more chance into the game. There's already enough chance for a natural 1 to be the death of your character without making players roll more often.
Also if everyone at your table really disagrees with your house rule, it's a good idea to listen. You and your players both have to work together to tell a story, and for that it's important for players to feel like they're being challenged without feeling like they're being punished. Especially if you can't use the excuse of "look, that's what it says in the book."