This page contains several diagrams for wiring a switch to control one or more receptacle outlets including a split receptacle and multiple outlets wired together.
Here a switch has been added to control an existing receptacle. The switch takes the hot from the middle receptacles. With this arrangement, all the other receptacles are wired directly to the hot source and the switch controls the middle outlet.
This diagram shows the wiring for a new receptacle added from a light switch. The switch must have an always-hot wire for the source and a neutral wire must be present for the return path. The hot source is spliced with a pigtail back to the switch, and to a new 2-wire cable running to the new outlet. The neutral is spliced in the switch box to both the existing light, and the cable to the new receptacle.
This diagram illustrates the arrangement for a 20 amp double receptacle circuit with a shared neutral wire. This arrangement is typically used in a kitchen where two appliance circuits are needed in close proximity to each other.