Objectives: McGinnis excels in tethering to objectives and peeling for teamfights. Use her abilities to stall out pushes, stabilize map state and empower team fights. McGinnis cannot typical excel without her teammates drawing enemy attention away from her. Because of this, her ability to break objectives or escape relies on her being highly reactive to map pressure.
Positioning: McGinnis typically does not want to be the first person enemies look at; This principle applies to both split-pushing and team fighting. She must watch minimap, or her teammates, and look for windows of distraction to act within. In teamfights, she should hover from the outskirts and provide suppressive fire or support. In a split-push, she must be decisive and never linger for long (She should clear wave, shoot an objective, and then run away before defenders arrive, or sacrifice her life to break objectives.)
Abilities: Each ability in McGin's kit is a tool. Turrets can force an enemy to waste a clip, or apply slow during a chase. Med Spec can be used to dig her heels into a zone, or empower a push forward. Spec Wall can be used to trap enemies in, or lock enemies out. She can build items into many different tempos, but generally, she is strongest when stalling out map pressure using her abilities.