If an ambulance is behind you and it has it's lights on and/or sirens you should try to pull over to the side of the road if possible to allow the ambulance to get past you.
If you're stopped at a red light proceed through the red light only if safe to do so. If it's not safe to go through the red light then pull out and turn in front of the car beside you to allow room for the ambulance to get through.
Sometimes an ambulance will be able to change the red light to green so pay attention to the red light as it might change.
Ambulance drivers are also trained to be able to get around you by driving over medians and other things when safe to do so.
If it's not safe to run the red light and pull out into an intersection then sit tight.
A well trained and true ambulance or fire truck driver will not try to push you out into the intersection and will wait patiently behind you until it's safe for you to proceed.
They do not want you to get into an accident yourself while they're in route to another emergency.