You can switch between any open applications on the Mac by using the App Switcher built into OS X. For more information, read the linked guide here.
Here is a great link with details on using Google Drive effectively for students. They include searching for scholarly articles, translating, and checking word count in your documents.
9 Things every student should be able to do with Google Drive
There are lots of free fonts you can download and install on your mac to use in multiple applications, including Pages, Keynote, and Word. Use this guide to learn the process of adding new fonts.
Adding New Fonts
Once you start a project in GarageBand, if you realize you need to change the tempo it is an easy change to make. Use this guide to learn how to change the tempo.
Changing Tempo in GarageBand
Use this guide to learn two easy ways to set up page numbers in Pages.
Setting Page Numbers in Pages