Plan ahead; brief your legal workers on appropriate state and federal statutes on police and federal officials spying. Discuss whether photographing with still or video cameras is anticipated and decide if you want to challenge it.
If you anticipate surveillance, brief reporters who are expected to cover the event, and provide them with materials about surveillance by your state police in the past, and/or against other activists throughout the country.
Tell the participants when surveillance is anticipated and discuss what the group's response will be. Also, decide how to handle provocateurs, police violence, etc. and incorporate this into any affinity group, marshal or other training.