Using wall-mounted shelf standards and brackets is an ideal way to increase storage. Here's an easy way to align the standards to ensure level shelves.
Start by screwing one standard to the wall; the screws should go deep into a wall stud. Install one shelf bracket into the standard. Take the second standard and install a bracket making sure it's clipped into the same corresponding slot as the first bracket.
Next, hold the second standard against the wall and place a level across the two brackets. Move the standard up or down until the it reads level. Mark the screw holes with a pencil, then screw the standard in place.