Post address & phone number by the phone for emergencies. Post your address at the end of your driveway.

Use a clear, calm, voice.  Don't rush your information.
State what the problem is & what help is needed.
While the dispatcher is gathering your information, another dispatcher may already be calling the first responders.

The dispatcher will ask key questions to ensure the right help is sent. Typical questions might include:

What is the address/location of the emergency?
What is the phone number?
What type of emergency is this?

Questions regarding domestic violence:

Is the violence happening now?

Are there any weapons in the house? Are others at risk?

Are there any injuries?  What are they?

Questions in case of fire: 

What is the location of the fire?

What is burning?

Are people trapped or hurt?

Where is the caller calling from?

Dispatchers will ask you what the injury or illness is, if  the  person is conscious, and what their age is?

Dispatchers can give instructions  to those administering CPR, treating minor injuries etc.

The more information you can give the dispatcher, the easier it is for him/her to prepare the first responder who is traveling to the scene.