Go to google.com/fonts to get started.
What I really like about this is while I’m choosing a font, I can see what a whole sentence looks like in that font. I can change the sentence if I want or I can see what the font looks like in paragraph form. Once you find a font that you like just add it to the collection. When you open up a new Google Doc you can select that font from the list.
So go to google.com/fonts and start choosing the fonts you like the best!