As this document is updated, I will mark the most recent changes with this highlight color.
The languages a starting PC can speak is determined according to the following steps:
Although able to operate freely with the benefits of armor, weapons, and magical items available to the classes the character is operating in, any thieving is restricted to the armor and weaponry usable by the Thief class. (see the Unearthed Arcana, pg. 22, and its errata, for the effects of armor on Thief functions.)
The multi-class PC will recieve the "better" of their multiple classes' number of initial weapon proficiencies, and will continue to gain proficiencies as per that class's rate.
All earned experience is always divided equally among the classes of the character, even though the character is no longer able to gain levels in one or more of the classes.
Hit points are determined with the following formula:
(HD for leveling class + Con bonus)/Number of classes
To determine Starting Hit Points, roll each class's HD 1, add the Con bonus 2, and then average the results by the number of classes.
1 respect Class-based Starting Hit Points minimum Hit Die rolls (see above)
2 respect Class-based maximum Hit Point Adjustement bonuses (see Player's Handbook, Constitution Table, pg. 12)
For Example: A first level Fighter/Thief, with a Constitution of 17, rolls a d10 as her Fighter Hit Die, and a d6 for her Thief Hit Die. Her actual die rolls are: Fighter[d10]: 7; Thief[d6]: 2. First, she would apply the Starting Hit Points minimums, arriving at: Fighter: 7; Thief: 4. Then she will add her Con bonus to both, respecting the Constitution Table's maximum Con bonus to Hit Point Adjustment (a Fighter gets a +3 with a Constitution of 17, but a Thief is limited to a +2). Therefore, we arrive at the following: Fighter[7+3]: 10; Thief [4+2]: 6. Finally, average the results by the number of classes (2 in this example): (Fighter[10] + Thief[6] = 16) / 2 = 8.
Note: when multi-classed characters are no longer able to progress in any given class, they no longer gain the hit dice for that class, but they still count that class in the divisor when gaining hit points for their other classes!
As per Unearthed Arcana, pg. 74: "If the initial ROLL of the die (or dice, for rangers and monks) is lower than the number given below, then the character is granted this number of hit points to begin his or her adventuring career" (emphasis, mine).
I'm interpreting that sentence to mean the following numbers are minimum rolls for a starting character. You should still adjust these minimums according to the character's Constitution-based Hit Point Adjustment.
Cleric 5 Magic-user 3
Druid 5 Illusionist 3
Fighter 6 Thief 4
Paladin 6 Assassin 4
Ranger 9 Monk 5
Though it is easily overlooked in the Dungeon Master's Guide, pg. 12, "For multi-classed characters use the column which develops the highest age and use the greatest possible addition to the base age; ie. do NOT generate the age variable by random die roll, but assign the maximum."
This, in effect, makes a Grey elf Fighter/Magic-user 180 (150 + 5d6) years old, while a Half-elf Fighter/Thief 46 (22 + 3d8) years old.
A.D.D.I.C.T - AD&D Intiative and Combat Table
I will be using this document as a reference during play and for better understanding of the rules.
Members of the thief class are not restricted to wearing only leather armor. However, a thief's chance of performing one of the special functions of the class may be lessened if he or she is otherwise attired.
See Unearthed Arcana, pg. 22 for further details.
Also, see the Unearthed Arcana errata
The "Class performance classification" system detailed in the Dungeon Master's Guide, pg. 86, will be followed when XP rewards are given out. As such, weapon and armor restrictions are not (usually) a hard limit, but instead directly influence the amount of time and money level advancement requires.
There are several exceptions:
I intend to utilize the modifications suggested in the Dungeon Master's Guide, pg. 82, in the section titled "Progression On The Combat Tables". In effect, the first '20' in any Combat Matrix can be obtained with any roll of the d20 and applied bonuses. The 2nd, and subsequent, '20's in any Combat Matrix represents a NATURAL '20' (the die must be showing a '20'), regardless of any to-hit bonuses.