So given the rules needed some filling in here and there, what were the ones I used at the table. These, for the uninitiated, are usually referred to house rules and include everything from simple rules clarifications to entirely new rules. There are a few things I always wanted to emphasize to players in my campaigns. There are pretty general but fundamental to the way I referee.
The referee knows things you don't! In other words, something may not seem to make sense (even within the given context of a fantasy milieu) but you have limited knowledge of what is going on. You're free to question an apparent error or oversight, of course, but be accepting if the referee tells you it is not actually a problem.
If you can conceive it, your character can try it. The campaign rules establish a matrix, within that framework you can try anything you deem necessary. All else being equal, for instance, a fighter cannot cast a magic spell; this is not something within the matrix. He could, however, attempt to pole vault a bottomless crevasse even though such an action is not covered in the rules.
Actions have consequences! You have freedom to act as you will but the campaign models a living, breathing world and there will be expectations of behavior your player-character is subject to. Sure, you can bully the shopkeeper and take what you want from him if you deem that a good idea. Just remember the town guard. And ... oh, yes ... isn't there a fighter and wizard of some renown staying at local inne who just might help bring someone getting too big for their britches to heel?
What would you do? Forget about what the rules do or do not say. If you were confronted with a tough problem within the game, how would you go about solving it. Forget about whether your player-character is a fighter or magic-user, how would a person confronted with this problem go about solving it with the materials and information at hand? Improvise, adapt, and overcome!
This is a game of exploration, not combat. You'll level up more quickly and lose fewer characters if you explore and obtain treasure while avoiding combat. Combat uses up valuable resources and grants a poor return in the form of experience points. If you can swipe the treasure from under the goblin king's nose? You'll score plenty of experience and not spend weeks recovering from your wounds.
Always a chance. Last of all? There are no sure successes or absolute failures in my game. The chances in either case may be small, but there is almost always a chance.