Fate inner-most concepts

Proactive: Characters in a game of Fate should be proactive. They have a variety of abilities that lend themselves to active problem solving, and they aren’t timid about using them. They don’t sit around waiting for the solution to a crisis to come to them—they go out and apply their energies, taking risks and overcoming obstacles to achieve their goals... (more linked above)
Competent: Characters in a game of Fate are good at things. They aren’t bumbling fools who routinely look ridiculous when they’re trying to get things done—they’re highly skilled, talented, or trained individuals who are capable of making visible change in the world they inhabit. They are the right people for the job, and they get involved in a crisis because they have a good chance of being able to resolve it for the better... (more linked above)
Dramatic: Characters in a game of Fate lead dramatic lives. The stakes are always high for them, both in terms of what they have to deal with in their world, and what they’re dealing with in the six inches of space between their ears. Like us, they have interpersonal troubles and struggle with their issues, and though the external circumstances of their lives might be a lot bigger in scope than what we go through, we can still relate to and sympathize with them... (more linked above)

Golden Rule: Decide what you’re trying to accomplish first, then consult the rules to help you do it.; This might seem like common sense, but it is called out because the order is important. In other words, don’t look at the rules as a straitjacket or a hard limit on an action.

Silver Rule: Never let the rules get in the way of what makes narrative sense.; If you or the players narrate something in the game and it makes sense to apply a certain rule outside of the normal circumstances where you would do so, go ahead and do it.

The Bronze Rule (aka The Fate Fractal; for GMs): In Fate, you can treat anything in the game world like it’s a character. Anything can have aspects, skills, stunts, stress tracks, and consequences if you need it to.

Unnamed rule (But let's call it the "Clay Rule"): Nothing is set in stone. You can leave parts of your character blank to fill in later, even when you just need it then. You can leave some of them rough to clarify later. You can even change every part of your character at certain milestones during game. (Though changing your High Concept significantly will probably be quite the role-playing experience.); Refer to: Quick creation and Advancement

Fun: We’re here, hopefully, to have some fun! Sometimes that doesn't mean what's best for your character.