* Use the latest White Box rules (PDF link)
By-the-book, with these changes:
* Max hit points at first level
* Fighters get a +1 BHB at first level
* Keep encumbrance simple, as per the rules, assume your 'standard' equipment weighs 10 lbs., to this add any armor and weapon weight and any coins at 10 per pound
* Fighters only get +1 to-hit and damage (melee or hand-hurled weapons) for a STR of 15+, all classes get -1 to-hit/dmg for STR of 6-, and +/- 20lbs carry capacity for the same values.
* A DEX of 13 or higher gives anyone +1 to-hit with missile weapons, 8 or less is -1 to-hit.
* Spell-casters get an adjustment of +/- 1 to the target's saving throw vs. spells, when it applies, for INT (magic-users) or WIS (clerics) of 15+ or 6-
* Holmes scroll rules - M-Us and Clerics can create scrolls of spells they know for 100gp per spell level and 1 week's labor
* M-Us begin play with a spell book containing all 1st level spells. Anything else must be found or bought. Clerics do not have spellbooks, they just pray for spells each day.
* Dwarves can see in the dark up to 60 feet, assuming no other light source brighter than moonlight is nearby.
* All players speak common. Clerics also speak their alignment language (law or chaos), which is more of a limited language used for religious ceremony. Other languages as per the rules, including the additional language for every point of INT above 10. I'll get a list you can choose from if needed.
* Halflings of average or higher intelligence (9+) can speak Gnome and Elvish.
* Bind wounds: Any character can bind wounds of another after a combat. This cures 1d4 HP, but can only be done once per day per PC.
* 0 HP is unconscious, death at -level HP unless another player binds wounds immediately after combat.
* MUs can use the dagger or staff as a weapon.
* Halflings and Dwarves cannot use two-handed swords or polearms.
* Elves get +1 to-hit with any pulled bow