It's all too easy to over-react when an emergency vehicle approaches - especially when a driver only notices the vehicle at the last moment.
If your first warning of an emergency vehicle that is close behind is the siren, you have not been checking your mirrors nearly as often as you should be.
Use your mirrors often - if you hear a siren in the distance look out for the problem, don't wait for it to find you! Scan the road well ahead and in your mirrors for blue lights and keep a look out for safe places to pull in if necessary.
When an emergency vehicle arrives in your vicinity your first reaction might be to brake... But this can cause problems if there is not a clear space for the vehicle to pass. Look for the safest option, a place where you can slow or stop with plenty of room for the driver of the emergency vehicle to pass. It's not usually a good idea to speed up or cross red lights to get out of the way - doing this can endanger you and others on the road.
Help emergency drivers and other road users by signalling clearly to show that you are pulling over. make sure that when you pull in you are not making things worse... For example, if you pull into a gateway or side road, check your mirrors to make sure that it is not the entrance that the emergency vehicle is heading for. Also avoid stopping om places where it will be difficult for the emergency driver to pass - for example, the brow of a hill oar a bend.
To sum up...
Remember that drivers of emergency vehicles are highly trained professionals - they will cope with any situation, but you should aim to help them, the best way you can do this is by staying calm and avoiding panic decisions.