So here are a few links to blog posts and essays by others on RPGs that I've found influential over the years. All credit to the authors of the originals!
An essay by Roger E Moore on making encounters difficult - and fun.
Many high-level characters have little to do because they're not challenged. They yawn at tarrasques and must be forcibly kept awake when a lich appears. The DMs involved don't know what to do, so they stop dealing with the problem and the characters go into Character Limbo. Getting to high level is hard, but doing anything once you get there is worse. ...
Don't Prep Plots
An essay on RPG story design by Justin Alexander
If you're GMing a roleplaying game, you should never prep a plot.
Everyone's tastes are different. These matters are subjective. What works for one person won't necessarily work for another. Yada, yada, yada.
But, seriously, don't prep plots. ...
On the same topic: Justin Alexander's essays on Node-based adventure design can be found here.
Getting the players to care
Another essay by Justin Alexander
I think every GM probably has a story about the time that they spent hours carefully detailing some piece of lore or a particularly intricate conspiracy... only to discover that their players didn't really care. Or you complete a dramatic and powerful series of adventures featuring the unraveling of a conspiracy wrought by the Dark Gods of Keht... but three months later you mention the name "Keht" and are met by blank stares from the players...
Decide to React Differently
(extracted from "Making Tough Decisions")
An essay on role playing by Rich Burlew, from Giant in the Playground
Have you ever had a party break down into fighting over the actions of one of their members? Has a character ever threatened repeatedly to leave the party? Often, intraparty fighting boils down to one player declaring, "That's how my character would react." Heck, often you'll be the one saying it; it's a common reaction when alignments or codes of ethics clash.
However, it also creates a logjam where neither side wants to back down. The key to resolving this problem is to decide to react differently. You are not your character, and your character is not a separate entity with reactions that you cannot control.