The most important thing in an emergency is ALWAYS to stay calm, most things are not as bad as they first appear.
No matter what kind of emergency, it is helpful to have the important phone numbers (vets) handy, as well as a list of what to do to help.
And please never forget that animals react differently under shock than under normal circumstances -> be careful, for your own safety!
In this helpful article by veterinarian Melina Lang, you will learn the most important symptoms and measures. A must read for every owner of a dog or cat.
Here you can download the article in PDF format.
Emergency medicine for small animals