As I have started a new campaign and am trying to be a better DM, I have decided to finally codify, after years, what exactly I award Experience Points for.
I first started playing with the Moldvay Red Box and have played every iteration of D&D since, even flirting with Next for a few games last year. We all know awarding XP has, over time, gone from an XP for GP model to an XP for killing monsters model. In 4e PCs even get XP for defeating level appropriate traps and puzzles.
It has always been my experience that when I do straight up XP for GP I end up with characters awash in gold. Even though they do have to spend their loot to cash in on its XP value, it just does not feel quite right to me. I do not want my games to be filled with millionaire adventurer-superstars. I want the PCs to be hungry for adventure... for loot... hell even for food. I prefer using other means to bleed off extra cash... like carousing (thanks Jeff), which does allow PCs to exchange GP for XP but with added risk.
I am splitting the difference. I am giving XP for loot extracted from dungeons, etc. as well as for defeating monsters, etc.
The outline of my XP system (updates will come in time... e.g. class based awards):
-100 XP per Monster Hit Die shared among all party members (Monsters must not be killed, just defeated: charmed, bribed, etc.)
-100 XP for a PC when he finishes off a monster
-100 XP for a PC when he cleverly defeats a trap, puzzle, etc.
-100 XP for a PC when he acts heroically, crazy, etc. and survives/succeeds
-25% of GP looted by a PC is converted to XP
I can keep my PCs cash poor while not bogging them down, keeping them from advancing.
Also, per my signing the FLAILSNAILS Conventions, my PCs earn XP in a per level method, zeroing out each time they level. See Jeff's update to Article 3. He has calculated the amount required to advance each level, making it simpler to calculate advancement.