From the Full Combat rules [B364]:

EVALUATE

This maneuver is the melee combat equivalent of Aim. It lets you take time to study an adversary in order to gain a combat bonus on a subsequent attack. You must specify one visible opponent who is close enough to attack unarmed or with a ready melee weapon, or whom you could reach with a single Move and Attack maneuver. You are sizing him up and looking for the right moment to strike. 

An Evaluate maneuver gives you +1 to skill for the purpose of an Attack, Feint, All-Out Attack, or Move and Attack made against that opponent, on your next turn only. You may take multiple, consecutive Evaluate maneuvers before you strike, giving a cumulative +1 per turn, to a maximum of +3. 

Movement: Step.

Active Defense: Any. This does not spoil your evaluation.

Also, from the Combat Lite rules [B325]:

Evaluate

Study an adversary to gain a combat bonus on a subsequent attack. You must specify a visible opponent close enough to attack or reachable with a single Move and Attack maneuver (see below).

An Evaluate maneuver gives +1 to skill for an Attack, Feint, All-Out Attack, or Move and Attack made against that opponent, on your next turn only. You may take up to three consecutive Evaluate maneuvers before you strike, giving a cumulative +1 per turn.