Introduce a culture of safety
A culture of safety should be created alongside considering what can be done to make it harder for a terrorist to conduct target research, such as introducing a policy for reporting suspicious behaviour. Staff are the most likely to pick up on odd or unusual behaviour, so encourage them to report anything that seems suspicious, whether this is a person themselves or bags left unattended.
To embed a culture of safety you should also be security-minded in your communications, particularly online. Include messages demonstrating your commitment to ensuring security and safety and avoid providing specific information that could aid in planning an attack, such as floorplans.
To ensure health and safety is properly embedded within your culture, risk awareness must be high at every level of your organisation. This means not only ensuring public-facing employees are aware of the risks, but that all levels of staff are aware and know what they should do in the event of an attack.