The following is a 10-Part series on Maya Beginner Basics. The tutorials are set up in-specific to game environment modeling.
Geometry Basics Exercise will help you to begin familiarize yourself with Maya interface, component mode, navigation and manipulating basic shapes.
Note: This is not how you would actually model a game environment. This is a basic exercise to help you manipulate basic shapes, use component mode, and navigate around the viewports.
Tutorial covers:
Using and Manipulating Basic Shapes
Building a basic environment out of basic shapes
Getting Comfortable with Maya Component Mode and Viewport Navigation
Use the reference provided above or select your own. Spend about 30 minutes and work on creating the environment from the reference using basic shapes. Getting comfortable with Maya's Interface.