Battle Focus (Bureau)
The Battle Focus abiliity is a key component to combat in The Bureau, as it not also is the interface for Agent and Ability commands, but also highlights enemies and equipment, contains a mini-map, and "slows down" time while in combat.
On Default controls, the Space Bar enters Focus mode, and both Space and Backspace can exit it. In combat: after selecting ability commands, and/or movement/targeting commands for your additional agents, exiting by pressing the space bar confirms those orders, while exiting by pressing backspace cancels the orders made during that Focus.
Most abilities, for either Carter or the other Agents, also require a kind of aiming (as well as commanding agents to focus fire on an enemy). For "tossed" abilites, like Area of Affect abilites or turrets, the camera will focus on the agent in question, who will have a highlighting circle of some diameter on the floor centered on him. This is the range that the ability can be cast at. Secondly, there will be a targeting hologram (in the shape of the cast ability) that must be aimed for it's area of influence (turrets will have a forward wedge to show what direction they will fire in, AoE abilities will have another circle showing the effect range).
For "Targeted" abilities (including when commanding agents to target a specific alien), a targeting 'scope' will usually snap on the closest alien. If you desire a different alien to be targeted, eitehr use A or D to go through availible targets, or aim with the mouse at your desired taget.
If you are in these aim modes, and decide you do not want to use the ability (ie; the alien is out of range, or behind heavy cover), simply hit Backspace to exit the Ability aiming without issuing a command for it. And, as mentioned, when in the top Focus mode, hitting backspace again exits Focus mode and cancels any other commands made during Focus.
Keep in mind the sequence that you select abilities does matter: having Carter use Lift on an alien to drag it out of cover first helps to damage it if you command a Recon agent to use their Critical Hit ability after. Another case where this can matter is when commanding an agent: if you were to command an agent to move, then go to issue an Ability command, you will find that the aiming of that ability will be from where the agent will be when he completes the move.
In effect; Battle Focus, ordering an agent to move ahead of Carter, selecting Lift and targeting a distant alien, and commanding the agent to use a AoE ability that would not reach from where he was, and hitting Space to complete the order becomes: The agent safely moves forward while the alien is immobilized from the Lift, gets into range, and casts his AoE ability, damaging the alien.