This video provides a good "day in the life" look at how a teacher could use Google Apps.
The demonstration of how this teacher uses the Google Calendar for lesson planning and scheduling meetings is particularly effective. You will also see how student can submit documents to the teacher as well as take quizzes using Forms. You will see how you can create a simple class website.
A great deal of information is packed into this 10-minute video. To embed what is presented here into your day-to-day life, I would suggest concentrating on one concept presented and watching the demonstration of that concept several times. Add one new thing at a time.
Are you using Google Apps? What are your favorite uses?