This installment of the 20 questions deals with the two big areas of bookkeeping: encumbrance and experience.
12. How strictly are encumbrance & resources tracked?
Countable resources (like torches): strict. Encumbrance: Loose.
13. What's required when my PC gains a level? Training? Do I get new spells automatically? Can it happen in the middle of an adventure, or do I have to wait for down time?
Must return to town to gain a level. Training is required for switching classes or gaining non-class abilities, but not for level increases. Spells must be researched.
14. What do I get experience for?
Treasure, defeating monsters, other.
I have been asking players if they are marking off torches and oil, but I should probably keep track of them myself as well. I haven't been tracking encumbrance very well, though. My intention is to only track it in terms of masses equivalent to the character: human characters can carry up to half their own weight at Move 9 or up to their own weight at Move 6, with anything more (up to twice their weight) halving Move again. But maybe I'll measure it out in "sackfulls". One large sack holds 300 gp, and the typical human is equivalent to 6 to 8 sackfulls. So, eyeball current encumbrance, figure out how many more sacks they could carry, and just count sacks.
Increasing levels and gaining spells are pretty much by the book. I figure if the character can switch to another class (prime ability 16+,) there's a restriction that the character must reach at least 2nd level in the current class and must go through some kind of training: find or purchase a 1st level spell book and learn how to cast spells, spend some time at a church or monastery in prayer, or train with multiple weapons. Figure the base costs for training equals the minimum amount of experience needed to gain your first level in that class: 2,500 gp for M-Us, 2,000 gp for fighters, 1,500 gp for clerics, 1,200 gp for thieves. This is the "crash course" price of training for 1 week; deduct 2,000 gp to become an M-U if you have captured a 1st level spell book, reduce the remaining cost based on the reaction of the trainer (i.e. they're willing to cut a deal,) and divide the cleric cost by the number of weeks spent in service to the church.
I'm pretty standard on what gets an xp award. Monsters: 100 xp/HD (but no adjustment for special abilities, so pick your battles!) Treasure: 1xp/gp, must be brought back to town and spent or otherwise ostentatiously displayed. I'm considering an additional award for other actions, probably a variant of the rule I've proposed before: base ability score x10 xp for extraordinary acts to impress others.