Encouraging Exploration

I somehow managed to poison myself with food. I feel like crap but you win because now I've got nothing better to do than make posts on my blog. Yay!

This question came from Facebook:

DMs: how do you inspire exploration in your games?

Again, a question that wouldn't even occur to me since D&D has always been about exploration when I played. This is the principle reason why 4e fell flat with me. But if you only started playing after 2000 (or, heck, possibly even after DUNGEON magazine started to become a bunch of stories the PCs were lead through by the hand, somewhere in the mid '90s) this might not be an obvious thing for you. So here are my suggestions for making exploration a central pillar of the game:

1. Mysteries: I give the PCs incomplete information, teases, or just straight up have an NPC tell them, "This is the way it is, and it doesn't make sense." Mysteries are an invitation to look for clues, and if they're compelling enough, become more important than levelling up.
2. Meaningful Options: it's not enough to just "Jaquay the dungeon". When you give players a choice, whether it's left or right, vanilla or chocolate, Zhent or Harper, make it immediately meaningful. By that I mean, in the passage to the left, you can feel a hint of a fresh breeze while the passage t the right has marks in the slime and dust of the floor that show something heavy was dragged that way recently. That gives you a mystery *and* a meaningful choice right there together.
3. Context: I'm very, very generous when giving information. Even when the players botch the knowledge skill rolls, I tell them something useful. To make decisions, players need information to base their decisions on, to gnaw on and argue about. There are almost always NPCs available that they can ask questions of.
4. Rewards: by the numbers, they might not be able to slay the rakshasa grand vizier, but if they know his weakness for smoked salmon, they might be able to bribe or distract him long enough to accomplish their goals. Getting an audience with the king is impossible, until you know his daughter has a collection of knives by one particular school of dwarven smiths. There's no way they can get to the Golden Mask of Zom by going across the volcano's open mouth, but if they explore some they'll find a way around, or a wounded aracokra who might fetch it for them once healed.
5. EXP: yeah, you can do this too. The earliest versions of D&D did this, for instance. It will mean contemplating what the PCs are going to do with the massive treasures they acquire (especially if you go with 1 gp = 1 EXP system but keep the EXP numbers as they are in the books). Traditional solutions include building and staffing strongholds, and carousing tables.

Art by Edgar Samuel Paxson.