Brendan posted these 20 rules clarifications that are likely to be needed at some point.
Here are the answers for my home campaign:
0. Base system? Pathfinder
1. Ability scores generation method? -- 2d10 6 times in order
2. How are death and dying handled? -- Die at negative your Con modifier (minimum 0).
3. What about raising the dead? -- Rare and not for sale.
4. How are replacement PCs handled? -- Roll one up and you're back at the next earliest convenience (beginning of next session at worst).
5. Initiative: individual, group, or something else? -- Group. PCs go in seating order.
6. Are there critical hits and fumbles? How do they work? -- 1 Fumbles (GM fiat), Crits based on weapon range as per d20 system (extra damage as described and extra effects when the GM feels like it).
7. Do I get any benefits for wearing a helmet? -- Yeah, head-shots are less likely to instantly kill you.
8. Can I hurt my friends if I fire into melee or do something similarly silly? -- Almost guaranteed.
9. Will we need to run from some encounters, or will we be able to kill everything? -- Run. Run for your lives.
10. Level-draining monsters: yes or no? -- XP draining
11. Are there going to be cases where a failed save results in PC death? -- Yes, and often.
12. How strictly are encumbrance & resources tracked? -- Very strictly, bring a spreadsheet.
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? -- Level up the next time you rest.
14. What do I get experience for? -- Good storytelling, creativity, sometimes for killing stuff.
15. How are traps located? Description, dice rolling, or some combination? -- Either/or.
16. Are retainers encouraged and how does morale work? -- Encouraged. Morale based on how well you are paying them.
17. How do I identify magic items? -- Trial and error.
18. Can I buy magic items? Oh, come on: how about just potions? -- Yes, if you have hundreds of thousands of coins and spend months searching for the right seller.
19. Can I create magic items? When and how? -- Take the feat(s) and start collecting body parts from monsters.
20. What about splitting the party? -- Yes, and good luck to you.