Useful Basic Operations
To extrude a set of faces, first select target faces using right clicks in face editing mode.
Then press "e" to start extrude. Move your mouse to decide extrude amount.
Finally, do a left click to finish extrude operation.
Scale, Translation and Rotation
Press "s"/"g"/"r" to start scale/translation/rotation. Move your mouse to decide amount. Press "x"/"y"/"z" to constrain your operation to be along/about corresponding axis. Finish with a left click.
Duplicate and Merge
You may only want to model half of a symetric object. The duplicate and merge trick will help you get the other half. (2:50~4:50) of the video tutorial shows you how to do it.