The basic movement controls are:
Forward: [ W ]
Strafe Left: [ A ]
Strafe Right: [ D ]
Back Up: [ S ]
To interact with an object or character, approach and press [ E ].
To take cover from enemy fire behind an object, move forward [ W ] and push against it. Shepard will lock into "cover mode" with back to the object. You can slide to the edges of the object using [ A ] and [ D ].
Near the edge of an object, it is possible to fire your weapon or use combat abilities. Shepard will appear to "lean out" to fire around the corner. If you are crouched behind a low cover object, you will "pop up" and fire over it. To leave cover, press [ S ] to back away from the object.
Irregularly-shaped objects may now allow you to move into cover mode behind them. Flat surfaces offer the most reliable cover.
Press [ Left Control ] to toggle into and out of crouch mode. While crouching, your weapons fire is more accurate, but you move slowly.
Press and hold [ Shift ] while using the movement keys to "storm" (sprint) for a short distance. While moving in storm mode, you will become fatigued - a bar appears in the lower left of the screen to show your level of fatigue. If you leave storm mode, fatigue will bleed away. If you run until the fatigue bar fills, you will be forced to return to normal movement speed, and will not be able to storm again until all fatigue has bled away.