Group steering can be broken down into three main steering behaviors: alignment, cohesion, and separation. An alignment steering force has the agent's face in the same forward direction as the rest of the agents in the group. Cohesion is a force that keeps the agents within the group together. Separation is the opposite of cohesion and forces the agents within the group to keep minimum distance from one another.
Using a combination of these three steering behaviors, which are also known as flocking, you can create groups of agents that are driven to move together yet not run into each other.