There's been an awful lot written regarding Game Mastering advice over the years, and some of it is very, very involved, and goes quite in depth. I think at times we can miss some of the simpler, more direct tools for helping to promote good GMing, and we get too bogged down in the abstract and the complex.
One of the things I was thinking about was in regards to Risk and Reward in gaming. Looking back at my earlier days of GMing, I used to run the super-easy, "Monty Haul"-type games. No shame in it; I'm sure a lot of us did. I threw out rune weapons left and right, even when I wasn't playing Rifts. Base kobold raiders were sources of uncountable fortunes in gems and gold. Even the lowliest mold or slime usually had a few invaluable tomes to give up. It was like the players were in a card game with a $10 million jackpot, only the card game was 52-Card Pickup.
When the pendulum swung the other way, it swung hard. Suddenly, everything was grim n' gritty. I was a Killer DM. A character couldn't take a leak without saving vs. death. Every seemingly innocuous roadside inn was trapped, and every proffered dish poison. Fortunately, I got called on this junk early, and it was a short phase.
It took me an embarrassingly long time to understand that most players want appropriate challenges. They don't mind the tough stuff, so long as there's an appropriate pay-off. As Jeff Rients once said, "give the players the sun and make them fight for the moon". You want to kill swamp rats all day for 1 tin piece each? That's great, but all you're going to have is a bunch of dead rats and an empty stomach (unless...). Oh, you want to be king? Well, that's great, but the Royal Seal was lost in the Mountains of the Moon three centuries past, and the current Pretender on the throne is a bloodthirsty immortal necromancer, and there's the small problem of his army of stone giants...
So we get to balancing risk and reward. This doesn't mean you have to give up the loot every time they kill something big. Rewards can also be social, emotional, political, or spiritual; material rewards are just a small part of the whole. That hill giant didn't have much loot, but damn if you aren't the hero of the entire barony now. Sure, you lost 3 henchmen and an eye to slay him, but look at you now!
One of the big things to balancing risk and reward is to really sell it to the players. They need to know the stakes, or at least the immediate consequences. It can be as simple as "if I don't kill X right now, X kills me instead", but it can also be more involved as "if I don't become King of the Skelds by winning Lady Y's hand, my competition will have me beheaded as a traitor to the crown". This risk should always be communicated. Without risk, there is no heroism, no bravery, and not much in the way of a memorable tale.
On the flip side, if everything is a risk, then it sort of loses its importance, doesn't it? When you have to congratulate yourself for not fumbling and killing yourself while shoveling a dung heap, true risk tends to recede, because at that point everything is risky.
Now, there are some people who want Monty Haul campaigns, or want to make every 5-foot jump an Olympian test. For those looking to find that happy medium, just remember your risk and reward. A simple thing, apparently obvious, but one that hits people hard.