Recently I worked on a project using Google maps. It was originally developed using Google maps API v2. I changed it to use v3 API.
Google maps v2 vs v3 API
Version 2 API requires you to register for an API key for every domain that uses google maps and must be inserted into the QueryString for the script reference. Version 3 API doesn't require an API key.
How to create a simple map?
1. First thing is to add the following script reference to your HTML page.
Note: sensor attribute is to specify whether your device has a sensor or not. (just to determine the user's location.
2. Create an object with the latitude and longitude co-ordinates. Simple map with NZ co-ordinates.