A Warrior may defend twice as many times as he/she can attack. Priests may defend once at level 1 to level 6, twice at level 9+. Rogues may Parry/Block once per round but Dodge as Warriors. Wizards may defend once per round. In no situation may a character attempt to defend twice against the same attack unless he/she is taking the "Turtle" maneuver. (see below)
The following is a list of basic maneuvers that would be available to a character on the defense.
For GMs who like smaller bonuses--like me: These bonuses reproduce the probabilities given in the AD&D game. However, they can be a touch unwieldy at higher levels. Therefore, a GM may want to halve all Attack and Defense bonuses (round down). This will give defense an edge.
*And Bards parrying (This compensates for the fact that Bards cannot back
*May use bonus while Dodging missile weapons.