When choosing fonts and making font combinations, you pretty much have two good options: use only one typeface, or use two that create contrast. Essentially, you don’t want to choose two typefaces that are too similar—that conflict. Here’s an example of each:
Also, here are a few good resources for creating font combinations:
Fontpair.co is a site made to show off some Google Font pairings.
The Web Font Combinator is a tool that lets you test combinations very quickly.
Just My Type is a collection of font combinations from a few popular foundries.
Font Flame is described as “Tinder for font pairing.” It’s great.