Triathletes who did not come from a swimming background can often have a tough time learning how to breathe in freestyle. I have written a couple of articles on this, addressing some of the major issues many people face with breathing.
This video shows a drill that adds a nice component to what we already know:
The important part here is getting that cheek to the shoulder. The swimmer in the video is obviously experienced so don’t worry about getting everything that perfect at this point, but this is a good drill to practice when you have advanced past the “building your balance” phase.