Story - I tend to put a premium on Good Story in my world. If you Role Play your Character well, and don't take foolish chances, then I find that tends to result in better stories. Meanwhile I try my best to build the back story based on literary sources and classical themes that tend to help bring out certain literary qualities into my game world. I have written up my actual game stories and posted them here: Elthos Example Games.
Drama - My games do tend to focus on interesting Characterizations and Drama, including romances, betrayals, and the great wide spectrum of human glory and folly. Definitely.
Exploration & Mystery - The essential plot lines of my world largely concern exploration, and the solving of mysteries.
By the Dice - I play above the table, open dice rolls, with the odds of winning stated in advance in most cases. However, that is only true for rolls where the Player Characters are involved directly. When it comes to behind the scenes things, such as whether or not a villain decides to sneak up from behind or wait until another day, I do those rolls without announcing their intent. Leaving those kinds of rolls a mystery for the Players, I find, enhances the game.
Tactical - Since I play by the Dice, it is considered good form in my world to consider the tactical situation and maximize your chances of success if you can.
Character Death - I do play by the the dice, and so Character Death is something that can definitely happen. That said, in the past, I've allowed some Characters the chance to escape Death's grip, and return from the Other World, so keep that in mind.
Run Away - Because I roll above board and stick to the outcomes indicated by the dice, and I allow for Character Death, Players are advised that sometimes discretion is indeed the better part of valor, and running away from insurmountable odds when you can is considered a sign of wisdom in my world. Of course, there is nothing wrong with a heroic death, when the end result is something worthwhile. And again, some Characters may simply feel that running away is cowardly, and so they will not do so, and thus take their chances. The odds of such Characters dying in combat is relatively high, but then again, they are more probable to be remembered as heroes by their posterity.
Use Your Brains - Player Skill is important in my world. If you can role play your Character well, then a lot of times you can make up for deficiency in particular Character abilities, work around them, or render them unnecessary. I put a premium on Role Playing over Gaming when it comes to the Story aspect of the game. Of course, that does not mean I will fudge skill rolls or allow players to succeed at skills they do not possess just to advance the story. But just like in life, play to your strengths for the best chance of success.
By the Book - I have a set of medium-weight traditionalist Character Generation rules, and relatively simple Conflict / Skills Resolution System, which I don't usually deviate from. The operative word there is 'usually'. I do not believe in *never* deviating from the rules, and so I allow for some (albeit rare) exceptions to existing rules, or modifying the rules over time when it becomes apparent that they are not balanced, or do not produce the desired effect.
Tinkering - While this may seem somewhat a contradiction to Playing by the Book, my rules are somewhat in a state of flux while I iron out the details based on actual game results (a very long process), though mostly stable, so yes, I am still in tinkering mode, and probably will continue to be for the foreseeable future.
Improvisation - I tend to improvise quite a bit on Non-Player Character descriptions, personality, and decision making. However, I will often know prior who the NPC is, what they are trying to accomplish, and what powers and capabilities they have, and strongly resist deviating from preset abilities. I also value Players who are able to improv their Characters as well.
Mirror, Mirror - Although it may not be obvious, I do absorb Player ideas during the course of the game, and may, or may not, reflect those ideas in the story over time.