Sorry For Your Loss
Before you go up to the door and knock on it, decide as a team which of you is going to make the actual notification, and who is there in a supportive role. By working as a team, you can more effectively help those you are notifying.
Take a deep breath, and say to yourself, "Be calm." If you are religious, offer a silent prayer for you, your partner, and the person(s) that you are about to notify, then knock on the door.
After knocking on the door, introduce yourselves and ask if they are the family you are supposed to notify. You want to be certain that these are the correct people to be contacting, the next of kin.
Then ask the resident being notified if you can enter their home. (Note: sometimes people won't invite you inside so you are left with no other option than talking to them through the door.). Once inside, if you can get the person(s) to sit down that is good, but not necessary. Because everyone is dumping so much adrenaline at this point, often people won't sit down until you tell them what is going on.
Ask as calmly as you can, and slowly while making good eye contact say, "Are you the parents of [Name]? I'm afraid that I have some very bad news for you..... (pause here momentarily to give those being notified a moment to psychologically prepare themselves). [Name] has been involved in a serious automobile accident, and he/she has died. (Pause) I'm so sorry. They did everything they could to save him/her."
Saying you are sorry expresses emotion, it makes you human. Continue to use the word "dead" or "died" throughout the ongoing conversation, and continue to use the victim's name. This helps those being notified come to the realization that their loved one has died.
Say the Word
Avoid using euphemisms. Don't say that their loved one has passed on....or "I know how you feel." Using dead or died is clear and to the point. When said with compassion, it is the best way to let someone know that a loved one is gone.
Avoid the "God clichés" such as "It was God's will" or "God never gives us more than we can handle." When we find ourselves reaching for these kinds of expressions, although well meaning, they are not generally helpful to those we are saying them to, and they often spring out of our nervous need to "say something."
Because of the life-altering bad news that we are sharing, it is important that we have the calm strength to "hold" what is often an emotional explosion. It is important to let them vent, and it is our job to ride it out with them, and to make sure that their reaction isn't a threat to themselves or others.
Remember to speak slowly, because in the midst of an adrenaline dump the people you're speaking with are not going to be thinking as clearly as they would under normal circumstances.
Maintain good eye contact. It's important for them to feel connected to you, for you are, in a very real sense, a lifeline to them in the midst of that critical incident.