As an early priority, organisers should establish that they can manage a crowd safely for the type of event and at the venue chosen. Even if the event is free or takes place on streets or open spaces, you should still apply the same crowd management principles to help make it as safe as possible. Once you have assessed the risks, you should create a crowd management plan. Use any venue/site design drawings to help you with this.
Stewarding and security arrangements should also be considered as part of your crowd management plan.
For full and comprehensive guidance: Health and Safety Executive