Ability scores generation method?
Roll 36 scores in order using 4d6, drop lowest. Take any six consecutive scores for a S/I/W/D/C/CH array. The end of the string wraps around to the beginning.
How are death and dying handled?
As per 1E's optional rule; death occurs at -10, bleeding out at 1hp/round or by any single wound that reduces HPs to -4 or fewer. Scarring or other bad stuff appropriate to the type of damage happen if a character reaches -6 or below.
What about raising the dead?
Spells or magic items; in practicality, 90% of the time it would be a raise dead spell. PCs who patronized the church or were held in great esteem by the masses as heros will have an easier time getting the spell. Others will pay market rates and may have to hunt longer for a caster.
How are replacement PCs handled?
Depends upon the situation, but most of the time they just enter the party and I leave it up to the players to explain it.
Initiative: individual, group, or something else?
Group, except spell casters who are not using wands or such; if casting a 1 segment spell they go with the rest of the group. 2-segment spells would go 1 segment after the group, and so on.
Are there critical hits and fumbles? How do they work?
This is up to the players. Monsters use the same rules. I have had players choose no crits, max damage on 20, 2 damage dice on a 20, and charts. The smart ones choose no crits.
Do I get any benefits for wearing a helmet?
It is assumed you are wearing a helmet if you wear armor. If you are not, than your head is AC type 10 modified by dexterity, and will be targeted half the time by intelligent creatures. I've never had someone buy a "great helm", but they could do so and get AC1 if they wanted to. I would just have to roll a d6 with the d20 every time they were attacked to see if it was against the head or not.
Can I hurt my friends if I fire into melee or do something similarly silly?
Sure you could. Smart missile use will target spell casters hanging back, or large-size creatures where it's not an issue.
Will we need to run from some encounters, or will we be able to kill everything?
Apex predators/monsters are at the top and bottom of most of my random encounter charts. Some placed encounters will be more difficult than the average for the area.
Level-draining monsters: yes or no?
Yes, but if groups make it a priority to avoid level-draining monsters they can usually do so, through information gathering or paying attention to clues (corpses in an area that appear to have died in extreme fright, or appear desiccated).
Are there going to be cases where a failed save results in PC death?
Yes; this is one way the fighter is balanced against the M-U - his saves are better after 3rd level. If you cut down on SvD, it gives an advantage to the wizard.
How strictly are encumbrance & resources tracked?
In practicality, during a gaming session not very often. If I think things are getting out of hand with equipment carried then I will request a re-calc. Or, when characters are trying to figure out how much treasure they can carry out they will re-calc.
Characters who are unencumbered for the combat and evasion advantages are kept track of more carefully, but this is easier because the limit is usually lower and they know exactly how much will push them out of a 12" movement range.
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?
PC M-Us get to pick any single spell they wish to learn when they gain a new spell level. I require training, but if a character doesn't have the gold they can work off the balance through a quest of some sort that is advantageous to the trainer.
I have allowed automatic level-ups in long adventures when I've ran them.
What do I get experience for?
Treasure, monsters, bringing the beer.
How are traps located? Description, dice rolling, or some combination?
Combination. A thief has an advantage in that it can find something even if the player running it doesn't know where the trap is, but is simply suspicious. Same with Dwarves and Gnomes in their abilities. Other classes/races can use description only.
Are retainers encouraged and how does morale work?
I don't push retainers on players, but I think if used wisely they are smart options for lower-level players. Treat and pay them well, and they'll have good morale. If you're also charismatic they'll have great morale. They work best as second-line polearm carriers, missilers, and spear-boys that keep the M-U out of melee, in my experience.
PCs who continue to use men-at-arms after about 3rd level will have problems keeping them alive as they fight more powerful creatures. If, regardless of all other factors, your retainers have a high death rate their not going to stick around.
Morale is rolled as per 1E DMG.
How do I identify magic items?
With an identify spell most of the time. I don't gimp identify by making it useless a few hours after the item is found, or require a live fish to cast it. It pretty much works although as per its description, it may not tell you everything. Legend Lore is useful for more powerful items.
Or, you can hire a wizard to do it for you when you get back to town; spendy though.
The time honored method of testing, trial and error can also work for those who are not afraid of cursed items or poison potions. Sometimes in desperate situations, you just gotta take a chance on that unknown vial and see what it does.
Can I buy magic items? Oh, come on: how about just potions?
I will usually make a few potions available by local hedge wizards and healers.
Can I create magic items? When and how?
Yes, as per 1E PHB for levels and spells necessary. The formula will vary from item to item.
What about splitting the party?
Up to the players; on a practical basis most don't want to have long periods of downtime in a session where they aren't the active group. So I've only seen it very rarely. But there are times where I think it's tactically appropriate to take the risk; and it is risky.