"Whatcha got in there? Blood? Yeeeeeeah, that's gonna have to go."
The first step to embalming someone is to check the paperwork, to make sure the person we have on the table is in fact the person we're supposed to embalm -- it is surprisingly common for the hospital or nursing home to give us the wrong body. After that, we disinfect the body and begin a process called setting the features, where we pose and manipulate the person's face to give them that "just sleeping" appearance. Since your eyes have a tendency to recess into your head postmortem, we put in little plastic cups called eye caps to avoid that sunken look. The caps also have little plastic ridges that dig into your eyelids to keep them from popping open during the viewing. While that would be considered hilarious in, say, an Adam Sandler movie, it's really the kind of thing we try to avoid.
Next, we take a device called a needle injector and shoot a needle and wire into your gums. We thread the needle around your upper and lower jaw (and sometimes up through your septum) to keep your mouth closed and centered. We also take this opportunity to pack your nose, rectum, and vagina (where applicable) with cotton to prevent "leakage" into the casket.
You'd be amazed at how watertight your body isn't.