Missile Ranges  Missile attacks are at normal skill up to the base Range; 1/2 chance up to 2x Range; 1/4 chance up to 4x Range.
Point-Blank Range  Missile attacks at a distance of DEX feet of less are Easy (x2). But if in combat, this is cancelled.
Shooting Into Combat  Divide chance to hit intended target by the number of combatants. A miss that would have hit hits a random target.
Targets in Cover or Darkness or Prone  Each of these conditions makes missile attacks against such targets Difficult (x1/2).
Damage Bonus  Missile attacks get only half the normal damage bonus from Strength. (Some missile weapon types get no damage bonus).
Parrying Missiles with Shield  Missile attacks by thrown weapons can be parried with a shield, or the shield can give a listed percentage cover. Missile attacks by projected weapons (arrows etc) cannot be parried, but shields can still give the listed cover. 
Parrying Missiles with Weapons  Missile attacks cannot normally be parried with other weapons.

Same Class Weapon Skills  Some similar weapon types can be used with the same skill, as noted on the Weapons list.
Similar Class Weapon Skills  Some fairly similar weapon types can be used with a similar skill as if Difficult (x1/2). Similar weapon types include:  Spear 2h & Polearm 2h; Mace, Hammer & Club; Staff & Club; Javelin, Dart & Throw; and all 1h & 2h weapon versions.

Non-human Sized Weapons  Damage, Armour Points, Speed, Space, Length x Scale; Weight x Scale^3. Scale = Species Height (ft) / 6

Light Sources  Torch 40' r. (4hrs/torch); Lantern 30' r. (4hrs/grease pot); Bullseye Lanthorn 80' beam (4hrs/grease pot).

Bleeding When on zero or less Hit Points a character must make a CONx5 roll every round to avoid losing a further 1hp by bleeding (or other deterioration). If the roll is CONx1 or less then the bleeding stops. Bleeding can also be stopped by binding the wound using the First Aid skill, or just staunching (i.e. applying continuous pressure). Bleeding caused by a Slash special hit can be staunched, but this causes all actions (attacks, parries etc) to be Difficult (x1/2) - although this type of bleeding will stop if a CONx5 succeeds.

First Aid  First Aid binds wounds and prevents further bleeding. If the First Aid skill roll is successful, it also restores d3 HPs (Special 2d3, Critical 3+d3, Fumble cause 1HP damage). For a First Aid attempt to be effective it must be the first form of healing applied.
Natural Healing  Each week of rest regains d3 HPs (alternatively, CONx3 per day to regain 1HP each. Rough treatment or exertion requires a CONx3 to avoid losing 1HP). Creatures of more than 1HD gain/lose in quanta equal to their Hit Dice.

Herb Lore   Finding, preserving and applying herbs and similar substances with marvelous effects. [Base WIS-10%, DF1]
Finding Herbs: Each 4 hours searching make a skill roll: Success finds 1 lot of herbs; Special 2; Critical 3; Fail 0; Fumble loses 1 lot.
Type of Herb Found: GM consults a Herb Table for relevant terrain or, if a specific herb is sought, the chance is 10 x Occurrence %.
Doses of Herb Found: 1 per 10% skill x d(Occurrence).  Applying Herbs: To effectively apply a herb requires a successful skill roll.
Preserving Herbs: Herbs only last a week unless preserved. A Herb Lore roll success saves 1 dose per 10% (S2; C3; Fail loses 1 dose). 
Minor Herbs: Minor herbs have many reputed properties (see DMG for details), however they are only 10% likely to be effective.
Locate Plants: Use of  this spell will allow a herb-finding roll every turn (instead of 4-hourly) and give a skill bonus of +5% per spell-level (i.e. per 1" diameter, as the bonus depends upon the linear dimension, not area, because the caster will be moving). However, when this spell is used, the druid (or other caster) is obliged by the powers granting the spell only to harvest every third specimen found. Also note that an occurrence roll must still be made to confirm each find, as a particular (plant) herb type must be specified. 

Weapon Immunity   Some creatures, such as werewolves, cannot be damaged by normal weapons due to their multi-planar nature. Fire is usually effective against them but falling, drowning, suffocation, poison, etcetera usually are not (except perhaps to subdue), although they can still suffer the effects of entangling or knockback. Such creatures can be hurt by magic and magic weapons, and perhaps by weapons of silver or 'cold' iron (i.e. pure iron, not normal steel), which inflict full damage. However, some such creatures will require special methods to permanently slay them (e.g. silver bullet, blessed bolts, stake through the heart, etc) or they will eventually recover.

Incorporeality   Some creatures, such as ghosts & wraiths, take no damage from normal weapons, which pass straight through them due to their immaterial and intangible nature. Magic may affect them, but only the magical component of magic weapons will do damage. Note also that incorporeal creatures are not blocked by non-magical weapons or armour - but they typically attack via Spirit Combat.

SPIRIT COMBAT  (aka PSYCHIC COMBAT)

Spirit or Psychic Combat occurs with aggressive ghosts/spirits, or between psionics, etc. Each participant attacks in turn by rolling:
Current Power (PP) x 5  modified by  +/-1 per Target PP under/over 10  :   Success reduces opponents PP by 1 (Special -2, Critical -3). 

When a participant is reduced to 0 PP they are defeated, and the resultant outcome depends on the circumstances:
 - If a spirit/ghost/demon defeats a creature with a material body, then that body may be possessed by the spirit (trapping the soul within);
 - If a spirit/ghost/demon is defeated, then it may be bound by the victor (if they have magical means to do so - otherwise the spirit escapes);
 - If defeated by a psionic attack then they will suffer effects according to the particular attack form used against them (see Psionics).

(Note: This is the usual saving throw mechanism but rolled by the attacker, enabling specials/criticals to be scored).