Malcolm Gladwell turned a lot of heads (as is his wont) in The Tipping Poing with the assertion/discovery that the main reason people become world class talents is not a result of inborn talent or expensive tools but rather on time spent. As a ballpark figure, it takes ten thousand hours of practice to really master something, and that level of investment takes a lot of work. Still, it's a kind of liberating statistic, since it suggests that the only thing separating you from Tiger Woods is time spent. Sadly, nothing is ever quite that simple.
One point that gets glossed over a lot is that they need to be 10,000 fruitful hours. That is to say, you need to spend those hours learning and improving. Receiving training from someone else, doing useful drills or exercises or even just paying attention to what you're doing in order to improve it are all fruitful ways to spend your time, and that's a lot of work. That's where things like talent, passion and resources start mattering - the guy who loves what he's doing, has a knack for it that makes him feel good about doing it, and has access to tools, teachers and time is going to rack up his 10k much faster than the one who is grudgingly grinding out the time. This is why simple mania doesn't result in talent.
For a GM or Game Designer, this raises an interesting set of questions like "How many hours have I logged?" or "When am I logging hours?" and it might be fun to dwell on them, but are really just proxies fro the more important questions of "how good am I, and how can I get better?"
Now, there are a lot of answers to this, but I thought I'd share a four of mine, specifically, what I try to do to make every session I play or run fruitful. It's never been an attempt to accrue hours, it's just been a useful approach. That Gladwell gives it a patina of legitimacy is just a bonus.
Check Your Tracks
There will come a time in almost any game when things go a little bit off the rails. Maybe it's just that you need to make an on the fly ruling but maybe you need to adjudicate something big and important that has no rules support. One that comes up a lot for me is making a decision to make an on-the-fly ruling rather than interrupt the flow of play with a rules lookup.
Be aware of the times you do this, and at the end of a game, look back and consider where your footprints wandered off the path. Then try to figure out why it happened and how well what you did worked. The situations you encountered will probably come up again, and giving this some thought will keep it from being an ad hoc solution every time.
This, by the way, is of particular interest when playtesting. When you're playtesting someone else's material, you really want to strive to stay on the path even more than usual because it's useful to the designer to know where you were inclined to (or forced to) deviate. You need to be even more aware of where your tracks would have gone so you can provide useful feedback. On the other hand, if you're playtesting your own material, you have a little bit more leeway. If a rule hits the table and you handle it somehow other than written, you really want to examine what you did because there's a good chance that that is what you really want in your game.
When a game breaks down it's easy to spend some time studying it, trying to figure out what went wrong and what could have been differently. But when you finish a great session where everythign went well and everyone had a good time, there's very little incentive to analyze. You need to overcome that instinct because there is as much (maybe more) to be learned in games that worked than those that didn't. Failure is easy to identify, but identifying causes for success is much harder, but much more fruitful.
So, don't necessarily dwell on it, but think about what worked really well, and ask yourself if you could do it again. Not every success will be something you can replicate, but over time you'll take lessons from what you find.
Value Feedback, Suspect Analysis
Nothing is more useful than talking to your players after the game . This is not just a good design thing, it's a good human being thing (that also happens to be a good design thing). You want them to tell you what excited and frustrated them, and you want to take that very seriously. This frustration and excitement is real - you cannot decide that one of you rplayers is wrong to have enjoyed part of the game or to have been bored during a part you thought was cool. That's how they felt, and you need to be ready to try to repeat or prevent that as appropriate.
The thing you should be skeptical of is the why. If your player was bored, take that at face value, but be a little more wary of any explanation of why they were bored or excited. As humans, we love to explain things, even if we're not very good at it. We'll create a narrative that makes things make sense to us out of whatever parts are lying around, and the truth of the matter may or may not have anything to do with it. This is not an attempt as deceit, rather a reaction to the fact that in complicated, subjective situation, the truth can be fuzzy, so we gravitate towards something that "makes sense".
This is not to say you should ignore their explanation entirely, especially if you know the player has good insight into what makes a game work, but it is ultimately your interpretation that's going to matter, and you need to trust that.
Do The Work
This one's simple - if you as your players to do something (like create a character) make sure you have done it already. The last thing you want is for your players to hit an inobvious roadblock (like unclear rules in chargen) that you just glossed over because they 'don't apply to the GM'.
1 - This is a hard lesson to learn, but an important one. Not for game design, but for interacting with people. If Dave says the fight was boring because the enemy had too many hit points you need to be able to balance your response so that you respect Dave's boredom even though he's totally wrong about why the fight was boring. The instinct is often to respond to these two things as if they were the same and treat Dave like the fact that he's wrong about the hit points means he's also wrong about the boredom, and yielding to that instinct makes you kind of a jerk (or a news commentator). It's also impractical, since you are training Dave to not give you any useful feedback. So, remember, respect the genuine underlying emotion, even if you discount the analysis it engenders.