Because of the very nature of the intricate and inter-related abilities and such of Advanced D&D, I have found it's much easier to modify the basic game and add in Advanced rules for flavor. Therefore, the remainder of this document will be devoted to tweaks to add to the basic D&D game, as given in the Rules Cyclopedia.

1. Weapon mastery- two words: use it. It allows for more interesting combat as well as giving more opportunity to illustrate character quirks or individuality. Remember that the character must seek out masters to train them and that there is a diminishing chance for success with each higher level of specialization. Grandmasters don't come along every day. As a subset to this suggestion:
   • make characters spend time and money (and possibly non-weapon proficiency slots) learning different anatomies. Example: a character who is an expert with a mace will receive the bonus vs. humanoids and common animals, but unless he knows the anatomy of a beholder, his mace will only do the normal d6 points of damage. This, too, will provide opportunity for better role-playing and combat scenarios.
   • the normal "to hit" progression goes out the window for characters, except for unarmed combat. If a character is going to do 2d8 with a sword and has a +6 to hit with skill bonus, does he really need to have the 15 THACO before strength bonus? Make the progression at 1/2 or 1/3 the normal rate, and combat will be more balanced.
   • allow monsters to specialize in weapons. This will make a third level fighter think twice before closing with the goblins (what if a goblin is a master with a spear vs. humanoids?). Create human or demihuman arch-rivals for the PC's that are equitable in weapons skills and in constant competition with them.
2. Spells- employ a spell point system based upon levels of spells available. Example: if a caster can normally cast two second level spells and two first level, she receives six spell points (2 for each second level, 1 for each first). This dumps the annoying rule that you "forget" a spell after it is cast and allows for greater flexibility as the occasion calls for it.
   • A high intelligence or wisdom, based upon the class, results in the stat's bonus in extra spell points for each progression on the saving throw charts. Example: a cleric with 17 wisdom gets 2 extra spell points until she reaches 5th level and receives new saving throw numbers. Now she gets 4 extra points.
   • Each spell requires the number of points of its level to cast (3 for fireball, 1 for magic missile), and spells above the level of the caster can be attempted. Suggestion for that rule: for every level over the caster's level, give the caster a -5 and have them roll a 20-sider. Modify the roll by the -5, -10, whatever; if the result is 1 or less, the caster takes an amount of damage equal to the level of spell attempted, loses the spell points, and the spell is not cast (but the caster can't do anything else).
   • Allow a user to "invest" herself in a spell if in a desperate situation. A well-played character in a back-to-the-wall situation can use inner energy reserves to cast a spell by sacrificing two hit points per spell point gained, half of the hit points being a permanent loss. This ensures the system won't be abused. And this can be used only once between meditations/spell study sessions (spell points must be regained between investments to reflect the draining effect on the caster). Example: a mage with two hit points left is cornered by an orc with attitude. Using his last two hit points, the mage generates one spell point and casts magic missile. He drops unconscious, the orc drops dead, and the caster has permanently lost one hit point (but not his life).
   • Consider using spells from AD&D as opposed to just the regular rules.
   • Make use of shamen and wiccas for monsters. Nothing surprises the party like the orc that puts them to sleep.
3. Experience - at least one third of all experience earned by an adventurer should be based on role playing, but if your players don't deserve it, don't give it.
4. Since there are avengers and paladins, consider creating a ranger class. It would progress with the same rate as a paladin, but would cast druid spells and be restricted from metal armor and certain weapons. Instead of holy abilities or undead turning, consider animal summoning or an innate ability to heal animals.
5. To increase survivability, give fighters (and subclasses) d10 hit points per level, clerics d8, and thieves d6. Also, give all 1st level characters maximum starting hit points.

Using these modifications, I have been involved in many D&D campaigns that were more fun and spontaneous than most, and more character-defining from a role playing standpoint. Try it once; you'll never go back.